In regards to sponsers; I had the same idea to fund my 2012 PCT trek. I sent out about 100 emails and letters to various outdoor manufacturers and distributers. I may have recieved 3 replies, saying thanks but no thanks.
The hiker/climber community is very close knit, everyone knows what everyone else is doing.
For the most part the sponsorships will go to the hikers with bigger names (IE-Scott Williamson). The guys that are thru-hiking in 60 days, or yo-yo-ing, or doing something bigger than just a 100 day thru hike. With that being said dont let that stop you from trying! It might behoove you to try to find a local sponsor that you can sit down with an owner face to face.
I can gaurentee that if you are a NBer starting mid April there will be plenty of help on the trail. Trail angels are an awesome breed of ppl, and will have food caches, beds, and other trail magic (BBQs at the trailheads!) waiting for all the hikers. They love what they do. Find a AT message board and start making friends with the Angels around the trail towns.
Steph, If youre in TX, the CDT would be closer to you, and perhaps save you some moneys on travel expenses. In my opinion the CDT is far prettier than the AT.
One last tip-Buy a dehydrator and start your stockpile now.