I recommend you start out trying to do something really monumental that interests you. After a few days of tinkering with it post your first draft here and 5 or 6 people will immediately tell you who has already done it better but would like some help. =) =) =)

More seriously, find a project that interests you and then try and find a module that does what you want. If so tear it apart and learn. If you can do it better or want it to do something differently, offer to work with the other author or send em patches or write your own module. I don't think you can just leap in and start whacking code on a site. Find something that you want to do and then look for others doing something similar.

If you already have a specific set of topics in mind, ask here. The monks are pretty hooked up with what others are working on.

--
$you = new YOU;
honk() if $you->love(perl)