MSN Gaming Zone:  Still up and running.  Free casual play and tournaments.  No ACBL.  No ratings so hard to find appropriate game.  Nice user interface for casual play - tournaments cumbersome with no auto-move and manual score collection. 

OKBridge:  The original and best online pay site.  Subscription required ($100/year), no free play.  Extra for ACBL ($50/year for 6 tournies per day)  Only online site offering stratified scoring .  By far the best software of all online bridge sites.  Largest subscription based membership.  Time tested accurate rating system (Lehman) - easy to find appropriate opponents.

Bridge Base Online:  Now largest online site.  Best free site on the internet with casual play & free tournaments. ACBL tournaments $1 each (most expensive on internet). Software functionality excellent - User Interface not the best.  Players self rated only so hard to find appropriate opponents.  Free Vu-graphs with commentary.

Swan Games:  Free & Pay site.  Casual play is free - tournaments require subscription ($80/year).  Exta for ACBL tournaments ($96/year for 3 ACBL tournies/day  or  $0.50/tourney).  If you only want to play in ACBL tournaments, you need not purchase a regular subscription. Small and friendly group.  Player ratings available for both free casual and paid tournament play.  Software functionality and user interface need upgrading.

JBridge: Free casual and tournament play.  No ACBL.  Software in Java.  Very small membership.