Leave it to soaring oil prices to make Web conferencing more attractive. Dimdim, an open-source meeting planning, announced Tuesday that its user base grew nearly 800% from last year to more than 500,000 people.

"In the last month alone, our users have spent more than 59 trillion minutes in Dimdim Web meetings. We’ve seen businesses, consumers, government and religious organizations turn to our free web meeting service to save money in this time of towering travel costs,” said DD Ganguly, CEO and co-founder of Dimdim, in a release.

Dimdim is simple and free to use. The Boston-based company, which launched September 2007, enables users to hold virtual meetings with all the requisite online meeting tools, much like WebEx. The difference is that Dimdim, which recently raised $6 million, led by existing investors Index Ventures, Nexus India Capital, and Draper Richards, is free. For premium services, Dimdim plans to charge. 

It seems pretty effective and easy. Signing up and setting up a meeting is quick and easy. 

When the meeting starts, you get an alert in your inbox to join the meeting.

You can also add features, or say how many people you want in the meeting. 

In the meeting, you can share a whiteboard, you can share PPT documents and PDFs, as you can see in this screen shot below. 

While it wasn't exactly perfect - for instance, I received error messages when I tried to share my desktop -- the service is free. And, you can't really beat that.