Omaha Poker & Omaha HiLo Poker
Omaha Poker is a similar kind of poker game to Texas Holdem but in Omaha all players receive four cards face down in the pocket, instead of two. There's still the same five community cards - but all hands must consist of two pocket cards and three community cards. To help you understand the difference between the games here's a basic guide from Sky Poker.
If you've played a lot of Holdem then don't assume that Omaha will be straightforward. The hands are different and things like pairs are not great winning combinations. The games can also turn considerably when the community cards are dealt simple because you have more cards to play with (9 as opposed to 7). Look out for straights and flushes rather than trying to put together traditional winning hands in Holdem.
You can also play Omaha Hi-Lo Poker at all the featured poker rooms. Omaha Hi Lo is played in the same way as Omaha except that the pot is split between the high hand and the low hand. Players may use any two cards from their hand to make a high hand and a low hand. If there is no qualifying low hand, the high hand wins the pot!