I use VLC and it is pretty easy. You can also do batches.
I've found the Firefox Firefogg add-on to be very useful (there are more encoding options than VLC or Miro, if you want to use them):
There's also an excellent plug-in for Adobe Media Encoder, available here:
Both are capable of producing excellent quality ogv or webm files.
Thank you very much for your answers!
Thanks for the info Joe. I forgot about firefogg, I guess because I am used to VLC. I should start using it and also try the plugin too.