This has been a bit overdue, but users who don’t want to use ClockworkMod recovery can now install zip files off their SD card using ROM Manager! (This is a Premium feature only.)
However, there are technical limitations that prevent full ROM Manager support for AmonRa recovery and such. These other recoveries need the proper hooks for ROM Manager to communicate with them and and do scripted installations and backups. But of course, ClockworkMod recovery is open source and can be forked and ported to new devices.