I play (When its for free) at
http://scorepoker.com/
I'll tell you why =)
There are i think 100,000+ people that have downloaded it, and you actually play for something. When you play on those big sites like partypoker etc, and your playing for free, people don't play properly. Hell, ive noticed people don't play properly until $5/$10 but thats me.
Anyhoo, download that software, and every Mon-Fri, you can play in the sit'n'go challenges. If you win one of those, you go to the finals (or semis, cant remember) and if you win that, you can win some $$$ ($150 for first i think) and you can also play in the multi tourney and if you place in that, you go to the final and can win a TV, some trips, and other swag.
So basically, if you want to learn to play, play there. You test yourself because you're actually playing towards something and teaches you not to be stupid, but costs nothing =)
And no, i do not work or have anything to do with scorepoker. I just think its a great place to practice/learn.
Check out the sched here:
http://www.scorepoker.com/tournaments/index.asp
Gives server list too.
Jayems.