What system should a user group use for event registration? Obviously they could role their own, but there are options out there so they dont have to. Some of them are covered below...
ClickTAttend - Microsoft owned system, functions pretty well, export user email lists, free, no option to charge for events -
http://www.microsoftgroupevents.com
CodeZone - User Group Support Services from Microsoft - a bit awkward but it will do - get UGSS atta boys for using -
http://ugss.codezone.com
EventBrite - Free service, good calendaring, used by many organizations out there - option for payment for events -
http://www.eventbrite.com
Meetup.com ($) - Costs to setup a site, wildly popular -
http://www.meetup.com