The following two websites will convert your videos into different formats online - without any software downloads - such as converting flvs to mpegs or avi files.
There are decent programmes out there to download that convert files and i imagine they are probably better at it and more customisable than online convertors however that's a post for another day once I've got my head round them all.
Yesterday I had to quickly change an flv into a format so that it could be placed into a PowerPoint presentation, unfortunately the video programme i have (Adobe Premiere Elements) won't import flvs (although it will export) and i don't have admin rights on my work PC to install programmes so i needed another option.
I first tried media convert which converts files 'while you wait'. You might have to do quite a bit of playing with the settings as some files don't convert particularly well into others plus the site isn't particularly user friendly. Anyway i successfully converted the flv into an avi and an MPEG that worked perfectly well. Also the site logo is a lizard or possibly a chameleon - lovely.
Secondly i also gave Zamzar a go which does the same thing as media convert except you provide an email address and a link to the file is emailed to you once processed. This is a lot cleaner and user friendly than media convert although to the point of making things so simple it seems to limit the amount you can do about the various conversion settings. I successfully got the flv converted to a WMV using Zamzar. And this site also has chameleons on it.
Take your pick, neither are going to set the world alight in terms of video quality or techie functionality but a quick life saver they might be.
Download YouTube clips and a bit about flv files (Nov 2007)