One of my friends is also trying to upload her son's videos up to her blog, but her camera captures videos in MOV format, I'm gonna guess it's using the Motion JPEG format. Anyway she was saying the files are too big to be uploaded. A quick Google would reveal a lot of video converters around, two that I've heard of (never used myself) are
Me? Well.. mostly my videos are edited in Windows Movie Maker since my camera outputs files in MPEG2 format and that mostly works perfectly with WMM. But if I ever had to convert videos, I just do it manually with FFMPEG. Problem is... you can't download FFMPEG in compiled form from the site, so if you want it you can pick it up here, I got it from one of the other compilation distro sites.
FFMPEG is a command line program and is quite intimidating to use, so read the documentation or.. here's a quick sample of a command that will encode a given video that should be small and suitable for upload to YouTube and such.
ffmpeg -i inputfilename.avi -vcodec xvid -acodec mp3 -b 300k -ab 64k -ac 1 -s 320x240 outputfilename.avi
That will take the filename called inputfilename.avi and will encode using the video codec of xvid with a bitrate of 300k and audio codec of mp3 with a bitrate of 64k, flattening audio down to mono and the outputfilename.avi will have a resolution of 320x240. If the results don't look or sound good, the use a higher bitrate value.