The best advice I can give after playing online for years, most of those weren't for money though.
I like bugsyclub they have lots of freeroll tournaments for points which you can use to enter other tournaments for actual money. Its slightly different to cash games but you will find them a lot more competative as there is something to win.
Also a lot of the prima poker sites have plenty of freerolls
though registration fills up really quickly from what i remember.
Or the other thing to do is play on the sites that have micro limit tables.
Final bit of advice I can give you is to FOLD FOLD FOLD, unless you have the nuts (best possible hand) you will often find bluffs don't work, if you don't have the goods or your starting cards are weak then don't play them.