Vaishakha Mahatmya

शाकं तु यद्वल्लवणेन हीनं न रोचते सर्वगुणोपपन्नम् ।। २७ ।।
वैशाखहीनं तु तथैव पुण्यं न साधुसेव्यं न फलाप्तिहेतुः ।।

Vaishakha masa is extolled as a month for earning great punyas ( Merits). Just as the delicacies we eat does not taste the best without salt, similarly without performing meritorious deeds (Satkarya and Dharmacharana) in the month of Vaishakha, one cannot savour the full taste of Punya.

This is the month of Snaana Daana and Japaa ( स्नानदानजपादिकम् )

तावत्पापानि तिष्ठंति मनुष्याणां कलेवरे ।
यावत्किलमलध्वंसी मासो नायाति माधवः २०।
This is the month in which we can purge and cleanse our systems of all the subtle doshas and Malas. That is why the month is "Mala-dhvansi" - destroyer of impurities.

वैशाखः सफलो मासो मधुसूदनदैवतः ।।
In the month of Vaishakha, Vishnu in the form of Madhusudana is worshipped. The destroyer of the daitya called Madhu. 

This month is also called Madhava masa. The month of Madhava. ( these subtle things become hidden in the kali yuga, based on the yuga dharma...that is why only few get to really know it, though this information can be found in many places, what to make out of it is never clear.
Vishnu is called Madhava because  -
1. he can be known through the knowledge of Madhu-Vidhya[According to Chaandogya Upanishad]
2. Ma = Lakshmi, Dhavaha = Pati) 

न माधवसमो मासो न माधवसमो विभुः ।
गतोहि दुरितांभोधौ मज्जमानजनस्य यः ६१।
दत्तं जप्तं हुतं स्नातं यद्भक्त्या मासि माधवे ।
तदक्षयं भवेद्भूप पुण्यं कोटिशताधिकम् ६२।
यथा देवेषु विश्वात्मा देवो नारायणो हरिः ।
यथा जप्येषु गायत्री सरितां जाह्नवी तथा ६३।
यथोमा सर्वनारीणां तपतां भास्करो यथा ।
आरोग्यलाभो लाभानां द्विपदां ब्राह्मणो यथा ६४।
परोपकारः पुण्यानां विद्यानां निगमो यथा ।
मंत्राणां प्रणवो यद्वद्ध्यानानामात्मचिंतनम् ६५।
सत्यं स्वधर्मवर्तित्वं तपसां च यथा वरम् ।
शौचानामर्थशौचं च दानानामभयं यथा ६६।
गुणानां च यथा लोभक्षयो मुख्यो गुणः स्मृतः ।
मासानां प्रवरो मासस्तथासौ माधवो मतः ६७।
तत्र यत्क्रियते श्राद्धं यज्ञ दानमुपोषणम् ।
तपोऽध्ययनपूजादि तदक्षयफलं स्मृतम् ६८।

The month of Madhava is uplifting, whatever is performed during this month as sadhana becomes "Akshaya", it is never destroyed.
The most revered among the devatas is "Vishvatma" ( narayana / hari),
among the japas it is gayatri,
among rivers it is ganga, 
among the feminine it is Uma,
among the tapasvis it is Bhaskara, the tapsya of Sun sustains the worlds.
Just as important health is to living beings,
Just as "paropakara" ( doing good to others) is the greatest punya,
just as nigama is the greatest vidya,
Omkara is the greatest among mantras, and
Atmachintana is among the dhyanas,
Satya is the highest of all dharmas,
Artha-shaucha among the shauchas, ( Earning through legitimate means and spending a portion of the earning selflessly for the collective good)
providing Abhaya is the greatest dana.
Being devoid of greed is the greatest among gunas,
similarly among the months Vaishakha is most important. 

Tirtha yatra, tapa, gyana, yagna, daana, homa, adhyayana all of this has great phala in this month
Tirtha snana is considered special in this month. 
Tirtha means sacred flow, having a mystical bath in any sacred flow is called tirtha snana. It can be in holy rivers which is in the physical level. Guru is the subtle flow, taking bath in the waves of wisdom is also tirtha snana. ( You can do swadhyaya and that in essence will be tirtha snana)

Since Vaishakha is in Grishma ritu, dana of "water" based things is very special as it is very useful for those who are tired and thirsty. Giving Juices, buttermilk, fruits, vegetables, anything that one can afford and offer to those who are tired and weary is to be done as seva.

Snaana and Arghya Mantras for Vaishakha Masa ( it is still uttarayana and surya is in Adana Kala)

।। ।। प्रार्थनामंत्रः ।। ।।
मधुसूदन देवेश वैशाखे मेषगे रवौ ।।
प्रातः स्नानं करिष्यामि निर्विघ्नं कुरु माधव ।।३३।।

।। अर्घ्यमंत्राः ।। ।।
वैशाखे मेषगे भानौ प्रातःस्नानपरायणः ।।
अर्घ्यं तेऽहं प्रदास्यामि गृहाण मधुसूदन ।। ३४ ।।
गंगाद्याः सरितः सर्वास्तीर्थानि च ह्रदाश्च ये ।।
प्रगृह्णीत मया दत्तमर्घ्यं सम्यक्प्रसीदथ ।। ३५ ।।
ऋषभः पापिनां शास्ता त्वं यमः समदर्शनः ।।
गृहाणार्घ्यं मया दत्तं यथोक्तफलदो भव ।। ३६ ।।

( the sankramana of surya from Mesha to Vrushabha rashi also happens in this month, that is why the arghya mantras are having the description of Rushabha as similar to Yama, the upholder of Dharma) 

The month of Vaishakha has the following Parva Dinas. 
The moola mantra ॐनमोनारायणाय ( OM Namo Narayanaya) can be used in worship.

1. Akshaya Tritiya ( Vaishakha shukla tritiya) / Parashurama Jayanti
2. Gangotpatti ( Shukla Saptami) 
3. Narasimha Jayanti ( Shukla Trayodashi) 
4. buddha Poornima

Akshaya Tritiya ( Vaishakha shukla tritiya)
Mangala snana, tirtha snana is performed. Fasting can be performed as per one's capacity, any other form of japa, stotra pathana etc can be done along with pooja vidhis. If akshaya tritiya falls on Krittika nakshtra, it is considered even more auspicious.

यद्यद्दत्तं त्वक्षयं स्यात्तेनेयमक्षया स्मृता । । 
यत्किञ्चिद्दीयते दानं स्वल्पं वा यदि वा बहु ।
तत्सर्वमक्षयं स्याद्वै तेनेयमक्षया स्मृता । । ३१
Whatever is given as dana on this day stays with us as indestructible merit ( Punya), this is why the tritiya is called Akshaya tritiya. 
The tritiya tithi itself is an auspicious day in general, but in the month of Vaishakha it has this special property of being "Akshaya". There are few other months too which have special days that are "Akshaya"

वैशाखस्य तृतीयायां नवमी कार्तिकस्य च।
पञ्चदशी च माघस्य नभस्ये च त्रयोदशी।। १७.४ ।।
युगादयः स्मृता ह्येता दत्तस्याक्षय्यकारिकाः।

Vaishakha (Madhava masa)- shukla tritiya
Karthika - Shukla Navami 
Magha - Poornima 
Shravana ( Nabha masa) - Shukla Triyodashi
Chaitra ( Madhu masa) -  Yugadi

This crazy fervour of buying Gold on this particular day is nothing but an encouragement of consumerism and spiritual materialism. 

ईश्वर उवाच।
अथान्यामपि वक्ष्यामि तृतीयां सर्वकामदाम्।
यस्यां दत्तं हुतं जप्तं सर्वं भवति चाक्षयम्।। ६५.१ ।।

वैशाखशुक्लपक्षे तु तृतीया यै रुपोषिता।
अक्षयं फलमाप्नोति सर्वस्य सुकृतस्य च।। ६५.२ ।।

सा तथा कृत्तिकोपेता विशेषेण सुपूजिता।
तत्र दत्तं हुतं जप्तं सर्वमक्षयमुच्यते।। ६५.३ ।।

अक्षयासन्ततिस्तस्यास्तस्यां सुकृतमक्षयम्।
अक्षतैस्तु नराः स्नाता विष्णोर्दत्त्वा तथाक्षतान्।। ६५.४ ।।

Ishvara says on this day, if Vishnu is just worshipped with "Akshta"( Rice), the merit gained is also like bathing in the flow of what is imperishable - Akshata :) 
Look at how simple, divine and soulful this is. 

Gangotpatti -
The descent of Ganga happens every year on this day but this is not the story of Bhagiratha bringing down ganga.
In Shiva Purana, there is the story of a Rishika who was following the Brahmacharya vrata very diligently. An asura by the name MuDha ( मूढ) was trying to seduce her and forcibly take her.
She prayed to lord Shiva and took refuge in Shiva. To protect his devotee Shiva descended as Nandikesha and killed the Asura. 
While shiva was blessings this Rishika with abundant devotion and purity, Ganga also manifested there and told the Rishika that she is inspired by her strength and purity. 
Hence from this moment on 
Every year on the seventh day of shuklapaksha in vaishaka masa Ganga will descend and those seeking purity will be benefitted. 

एतस्मिन्समये गंगा साध्वी तां स्वर्धुनी जगौ।।
ऋषिकां सुप्रसन्नात्मा प्रशंसन्तो च तीद्विधिम् ।।२८।।

गंगोवाच।।
ममार्थे चैव वैशाखे मासि देयं त्वया वचः ।।
स्थित्यर्थं दिनमेकं मे सामीप्यं कार्य्यमेव हि।।२९।।

सूत उवाच।।
गंगावचनमाकर्ण्य सा साध्वी प्राह सुव्रता।।
तथास्त्विति वचः प्रीत्या लोकानां हितहेतवे ।। 4.7.३० ।।

आनन्दार्थं शिवस्तस्याः सुप्रसन्नश्च पार्थिवे ।।
तस्मिँल्लिंगे लयं यातः पूर्णांशेन तया हरः ।।३१।।

तद्दिनात्पावनं तीर्थमासीदीदृशमुत्तमम्।।
नन्दिकेशः शिवः ख्यातः सर्वपापविनाशनः ।।३३।।
गंगापि प्रतिवर्षं तद्दिने याति शुभेच्छया।
क्षालनार्थं स्वपापस्य यद्ग्रहीतं नृणां द्विजाः ।। ३४ ।।

 This day is the best "Tirtha" one must wash away their negative tendencies and misdeeds on this day and take the benefit of the active powers of Ganga on this day. Even if you mentally think of this active presence on this day, you are benefitted by mere "sannidhya", proximity. 

Narashimha Jayanti -