This plugin by Kunal Bhalla allows creating custom registration forms, a calendar for listing out events, and provides inbuilt themes for the default themes for WordPress and BuddyPress, which can be over-ridden as required.
Requires WordPress Version: 3.0.0 or higher Compatible up to: 3.0.1
For this plugin to work properly in BuddyPress, you need to install BuddyPress Custom Posts.
Download: http://wordpress.org/extend/plugins/eventpress/