The Stardeck
Here's a kinda interesting link I had forgotten about: www.stardeck.com. The Stardeck is an 5-suited deck. The 5th suit is stars.

I ordered two of these Stardecks about 3 or 4 years ago when the only poker I was really playing was .5/.10 wild-card games with some friends from college. It was usually B, me, and 3 other couples, so that made 8. A lot of the crazy wild-card games are 7-Card Stud variants, and as the Stardeck website proclaims, the Stardecks can be used to play 8-handed 7-card Stud. However, it does throw the poker hand ranking off a bit, since with the 5 suits flushes are harder to make than full houses. The Stardeck website also has suggestions for Stardeck-only poker variants.

I haven't used my Stardecks in a while, but now and then I get the urge to when it gets late and punchy at our home game. Three of four years ago they were a hit, as everyone enjoyed the novelty factor. But I haven't spring them on anyone since the poker boom really started, and I bet I'd be more likely to run into a self-proclaimed purist snubbing his nose at the poor Stardeck :-)

I've also heard of nautical-themed six-suited decks, in which the 5th and sixth suits are blue anchors and ship's steering wheels. Haven't been able to track one down though.
posted by James at 5:36 PM