There was some proper old school poker movie someone mentioned in the chatbox but I can't remember what it was called now though (actually 'A Big Hand for the Little Lady' I think it was called, found it via Google!). Not actually seen that though, would probably have to go out of the way to try and find it I think...
I guess 'Rounders' is the obvious one and a good 'un too.
I watched '21' last year on youtube on a lazy Sunday morning (10 or 12 ten minute clips), because I'd read the book ('Bringing Down The House') which I really enjoyed. Its about the MIT blackjack team. The movie is enjoyable enough but I think the book is better.
Watched a more recent one (made in the last 3 years) about a poker rounder who stole from his girlfriend in order to enter the WSOP. Then plays a cheesy and weird hand against his father at the end......what is it called?
I remember a tv series in the eighties when I was a lad called something like Big Deal (I'm not too sure that's right, I might be confusing it with the Anthony Holden book). There was this poor sap who was always losing his shirt at some poker game or other.
As for films I was recommended Big Hand for a Little Lady by Fella in the chatbox a while ago, and it is an excellent, funny, brilliantly performed piece by some legendary old school film actors.
The one mentioned above is a rather dismal flick called Lucky You, directed by the normally brilliant Curtis Hanson (LA Confidential, The Wonder Boys, 8 Mile) and starring Eric Bana, Robert Duvall and Drew Barrymore. Lucky You (2007)