If you are looking for a browsable round-up of web conferencing platforms and their main key characteristics and traits, you can take a pick at this article-report from Social Business Today.
It lists 15 web conferencing services while providing some useful complementary information for each one, including key features, availability of a trial, and pricing.
Consider this a basic reference to get an idea about differences between major services, but do not rely too heavily on it as my impression is that it is not fully updated and some of the info there contained is actually not correct or incomplete (pricing without correspondent information on what relative capacity it affords is useless) (I am also a bit skeptical in relying on sites that do not provide clear author info).
Still, if I had someone just ask me now where he could find a basic reference for some of the available web conferencing solutions I would suggest them to take a peek at this article.
...and if I had to make my recommendations among those listed, these are the three services I woud suggest you to consider:
a) GotoWebinar - my choice and favorite (yes, it's too expensive)
To see ALL of the best online collaboration tools
please check: www.mindmeister.com/12213323
(Reviewed by Robin Good)