Like Zamzar, youconvertit provides web-based file conversion. You upload audio, video, image or document files and convert them from one format to another. All you need to do is select the file from your computer, select your target format, and the file will be uploaded and converted. Once the conversion is complete, you receive an email link to download the converted file. youconvertit stores files for 7 days, compared to Zamzar's 24 hour storage.
Unlike Zamzar, youconvertit does not have a file size limit (that may change once youconvertit emerges from Beta). Furthermore, you can convert measurement units like size, area, distance, time, velocity, mass, and it has an online media download manager for YouTube, Metacafe and Google videos. To download videos from YouTube, Metacafe and Google, just enter the URL of the file and then either convert it directly or download it to your computer.
Both Zamzar and youconvertit are tremendous productivity enhancers. What file conversion tools do you use?