Have a read of this person's experience marketing an iPad app:
http://www.shindigital.com/blogpost/74
Check out the other posts on his blog, too. They might be helpful.
Ask HN: Any ideas about increasing traction for a socially-oriented app?
11–12 of 12 posts
Re: Ask HN: Any ideas about increasing traction for a socially-oriented app?
#12http://www.seomoz.org/blog/the-noob-guide-to-online-marketin...
is an amazing resource