iPROConference rental is $39.95/month, $119.99 for 3 months.

The most popular web meeting solution WebEx MeetMeNow (from Cisco Systems) can be rented for $39/month.

Both iPROConference and WebEx MeetMeNow are services, not software that you can install on your own server. The good thing is that you don't need any special knowledge on servers, installing and supporting server software.