XDA forums for the Captivate. Most are really good, but here is one that has been running excellent on my phone, [ROM]JW1[2.3.6] SAUROM Projekt 'One Rom to Rule Them All'. DAGr8 has put together a stable, fast performing build with this release. It includes tons of lock screen and toggle options, as well as a great selection of themes.
One thing that makes this ROM great is the Semaphore Kernel included in the package. I run over clocked @1200 and the responsiveness is impressive.
A Heimdall One Click is available for an easy installation as well as the usual CWM flashable zips.
ADWLauncher EX. The clock and live wallpaper are both from Beautiful Widgets.