Here’s a Useful Site to bookmark; youconvertit.com.
Free! Convert any media file format (Documents, Images, Audio, Video & Archives) without buying or installing anything on your PC
All you do is upload a file, tell it what format you want it converted to, and it’ll email you with a download link when it’s done. Of course, there are limits to what it can do — MS Publisher files are out of bounds for some reason (Zamzar will do .pub files) — and you certainly don’t want it converting something that contains sensitive or personal information. But for that oddball file that gets emailed to you that you can’t open or convert on your own, it’s great.
And it doesn’t just convert files; if you see a video online, whether it’s on YouTube or just in a weird format, and want to be able to download a copy, just go to YouConvertIt.com’s Video Conversion page; paste the link to the video you want converted, and click the button. In a short while you’ll get an email with a download link. Very slick.
And that’s not all; there’s a separate section that does just unit conversions. Granted, the interface is a little clunky and I can do the same thing and probably more quickly with the Calculator that comes with OS X, but for those times when I need to convert something that Calculator doesn’t handle (like a parsec, which is 19,161,519,629,164.8 miles), it’s pretty darned helpful.