I can often be found on the Free Internet Chess Server (FICS) where I mainly play three-minute blitz games or three-minute crazyhouse. "Three-minute" means that each player has a total of three minutes to make all of their moves. This makes a typical three-minute game last about five minutes which is about the length of time commitment I can afford these days.
Crazyhouse is a chess variant where whenever you capture a piece, it changes over to your side and can then be placed, at your discretion, anywhere on the board. It leads to a very aggressive game where positions tend to rapidly "blow up".
Hostage Chess on the other hand is similar to crazyhouse in that captured pieces can come back on the board, however, they do so in a more controlled and equitable manner which leads to a game with more of the contemplative feel of regular chess. Hostage Chess is not yet playable on FICS, but I would like to see it implemented there.
Questions or comments?