Several websites are offering hacks for freemyapps, and you will need to browse through each one to see which best meets your needs. All these sites recommend you only use these hacks once every couple of days, in case your account is suspended.
fma-hint.blogspot has a link available to those who have not used freemyapps before to enable them to get extra credits, and for those who have already used freemyapps, a program to install which depends on your having a jailbroken device and the UDID faker found on Cydia.
Stafaband.info has a MP3 downloadable hack for Freemyapps which can get you 40,000 free credits.
Pastebin.com has a page of raw data to use for hacking Freemyapps and claiming 50,000 free credits.
Youtube is a good place to look for hacks. Here's one you might like to try: