Check out Zamzar. This web service will freely convert documents, images, music, video and even CAD files for you. The free version limits you to conversions of no more than 5 files at a time and they must all be smaller than 100MB. If you need larger files, pay plans start at $7 per month.
Be warned, the site is ad supported so expect pop-ups and flashing banners everywhere. Otherwise, if you just want to convert something into a format you can use, Zamzar is great.
What do you think?