I've finished up my work on connection pooling, patch is here:
http://rails.lighthouseapp.com/projects/8994-ruby-on-rails/tickets/936-connection-pooling
Please try it out, comment, etc. and give +1s if you want. Any comments on default pool size (5) or default wait timeout (5 seconds)?
Note that this is probably not the last word -- the patch still needs to be battle-tested, but we expect that to be done once the patch gets merged into edge and any necessary fixes will follow.
Cheers, /Nick