In my opinion, the best capture/conversion program for web video is DownloadHelper
It has rarely failed to capture the video. I don't use the conversion part much but it had done the job when I have used it.
I use this free extension with Firefox (I think there is a Chrome version). It will capture video clips as well as audio only from sites. Most of the time I just start playing the video/audio on the web site and click the DH button, click Save and let it do its thing. You will get a little nag box every 500 captures.
For some sites that DH doesn't work, I use the previously mentioned RealPlayer SP. The main thing I dislike about the program is that it creates a library and makes it difficult to store videos where I want. It has conversion capabilities but I don't know how many formats are supported. Hope this helps.