Head on over to DRay's Bay for a detailed breakdown of the deal from the Rays' perspective.
Myself, I think this trade is several years overdue for the Rays, and rather interesting for the Astros, the team we're really concerned about.
Houston sent down Jason Lane to make room for Huff. Lane is having a legitimately awful year, hitting only .205/.330/.393, but isn't nearly that bad and would be an excellent pickup for some team buying low at this point. The Astros' other corner outfielder, Preston Wilson, is also struggling, at .284/.322/.424 and both he and Lane are playing horrible defense. Mike Lamb has been hitting very well lately, so I'm thinking that Lance Berkman will see most of his time now in RF rather than 1B, with Lamb starting at 1B and Huff taking a lot of at-bats from Wilson in LF.
Bottom line, this trade makes the Astros a better team this year; with Huff & Roger Clemens, they're probably a better team than the Brewers right now.