I'm racking my brain but for the life of me I can't remember the site I used to use for these exact questions. There was a site that was almost entirely devoted to video and audio conversion, and had an extensive database of all the software out there. It even had a tool where you could enter the source and target formats and it would return a more-or-less accurate list of tools that could do the job, with links to the sites that hosted them.

It's been ages since I did much encoding at all, so I can't recall what the site was. I think that once I discovered Handbrake that took care of most of my conversion needs.