Games
MLB Home Run Reaction Time here - are your reaction times fast enough to hit a home run in the majors.? :)

Play Catch here - a hybrid game of cricket and baseball, a league has been set up for Brentwood Baseball Club at the link, don't be shy to invite your friends to join. :), Good to see a few people are playing :) League table here

Multi-player online baseball can be found here, haven't tested it much yet, but feedback elsewhere is very good. Recently updated for 2007

Facebook
Brentwood Baseball Club now has a group at Facebook, here

Main Baseball Sites
British Baseball Headquarters here - information on the BSUK and BBF

UK MLB supporters Club forum and articles here -

MLB.com here - for a huge repository of statistical information about baseball, both past and present, many articles, mainly but not exclusively from an American perspective, and all the US baseball games live for viewing for £10 a month.

Technique
Webball.com here - for all aspects of technique from pitching, hitting, throwing, fitness, drills

Baseball Tips here - similar to webball.com, covering all bases

Be a Better Hitter here - self explanatory

Batspeed here - a forum looking at the speed and rotational aspects of batting

Fitness and Injuries
Peak performance here - not just baseball related, but with a lot of specific baseball articles, on performance, fitness, speed, power injuries etc. It also links the similarities between sports, ie overlaps in speed training, power training from a speed perspective,...Heavily scientific, not based on just anecdotes. This site is used by serious athletes

Sports Injuries here - again very scientifically based, not anecdotal

Umpiring
GB Umpires Site here

Umpires perspective here - an interesting article on the visual perception of umpires from a scientific research project

Statistical Analysis
Baseball Prospectus here - one of the main baseball statistics sites, covering all aspects of the game

Hardball Times here - statistical analysis and more general articles

Baseball stats in a graphical format here - Fan Graphs is more accessible than some other statistical sites because it uses a lot of visuals

News and Blogs
Strike Two,net here - encapsulating 688 baseball blogs
Curt Schilling's refreshingly honest blog here, this should be a fascinating read as the season develops.