I have been experimenting with a completely free piece of software for the last few months, that actually does a reasonable job of converting (also batch conversions) most video file formats to popular mobile and PC versions. Its called FreeStudio, but why is it free? According to the website they make their money out of advertising from an installation of a navigation bar that appears in your web browsers... However I will point out that it is possible to deselect the install of this web bar in the early stages, and would recommend doing so. When you see the option to install this web bar, ensure you have unchecked from the bottom up, none of them should be selected. If you do forget, it is possible to un-check it from showing in the 'settings' area of your browser.
Ok, that bit out of the way... The software is pretty comprehensive and there is even a screen capture software (currently without sound) that does a very good job. Most of the video converting areas are geared up to converting from DVD to video file formats, (you can only do this with DVD's you have permission to copy, of course)
The 'Mobiles' area allows conversion from just about any file format to a format specific to that device. Batches of files can also be converted to a reasonable MP4 video format using for example, the 'video to Android' and selecting a resolution that suited my needs. The options for quality of rendering: economy, standard or high are available. Standard is pretty good for most needs, if you are using a small screen economy is probably good enough for most. So far I can say outputs work great on my HTC android phone using standard quality setting.
There is nothing strictly for any video to PC use, although I actually found the MP4s from the mobile conversions worked well on PCs. I think the trick is to use the mobile converters and select an output resolution that is closest to your needs on the PC.
It's certainly worth looking through all the various options available, as the programmers have made a big effort to keep the interfaces simple and easy to use.
Yes you can capture some video streams from the web...What I will remind users is that capturing media from the web without the correct permissions from the original authors is most likely in breach of copyright (on many levels - hosting company, creators and owners). Ensure that there is some creative commons licence (or similar) associated with its use. The commonly used version is attribution-non commercial (which is fine for educational use). Avoid Share-alike, unless you wish to distribute your work with the same licence (it's a requirement for using this creative commons agreement I'm afraid). For all other materials, assume that you cannot use it to be on the safe side. The other option is to contact the owner and ask...
Oh and there is even some interesting 3D converters they are developing, but needs the traditional glasses for it to work... ;)
A big thank you to Freestudio for an excellent set of resources. I hope to see many more developments in the future!