What usually works is to simply google the package name and add maemo to your search string. Id est: searching for libc6 and maemo will return an address like maemo.org/packages/view/libc6/‎.

Provided you have the correct repo's enabled in HAM or FAPMan it should work there too. But the default app manager (HAM) is so terribly slow I prefer the command line above anything else.

Edit: Typo's (Not used to my new steelseries keyboard just yet)