Having featured some free media and file conversion tools and services in a few earlier posts…
A free file convertion service that will handle files up to 100Mb in size. It can convert a fairly large range of document, image, music and video formats.
All you do is pick the files you want converted, select a format to convert them to, enter your email address and hit the Convert button. Within a few minutes you'll receive an email containing a download link for your converted file(s). You can convert up to five files at a time and Zamzar will hold the converted files for 24 hours before deleting them.
I tried it out with a 4.8Mb PDF and it converted it to an MS Word .doc file very quickly. Okay, it wasn't exactly spot on with the page layout but all the elements were there and I could edit them all easily. I also converted a Flash movie (FLV) to a QuickTime MOV file and it did it perfectly.
This is a free web service that is available to anyone who uses diagramming software and has a requirement to open Microsoft Visio (VSD) documents. This service was been created because Visio users often don't save their drawing into Visio XML (VDX) file format, which is more portable. They typically send files as VSD documents, often making it difficult to read them by other diagramming software packages such as ConceptDraw, which is quite popular with Macintosh users as Visio isn't available to them.
Converts a small range of audio, video, MS Office, image and text file formats. Not an all-encompassing service but there are a few useful converters in there. For example, you can convert AVI or WMV files to an animated GIF.
A maximum file size of only eight megabytes makes it a bit limited though.
Vixy FLV Converter
This one can convert Flash movies (FLV), like those you'll find embedded on video sites like Youtube, to another MPEG4 format - AVI (DIVX + MP3), MOV (MPEG4 + MP3), MP4 (MPEG4 + AAC), 3GP (MPEG4 + AAC) and MP3.
All you do is submit the URL of the web page with the embedded movie and it'll convert it for you and then offer you a link to download the converted file.
A mixed bunch this one. There's a collection of various converters for text file end-of-line characters (Unix2DOS, DOS2Unix, Mac2Unix), PDF text and info extractors and some data file format converters (.xls to CSV, fixed record length to delimited and vice versa and CSV to delimited).
So, to sum up, I'd definitely recommend Zamzar and Media-Convert for general file conversion services. The others listed are more niche or specialist focused but could be useful if the need arose.