Media-Convert.com allows you to convert Audio, Video, and Documents for viewing on your BlackBerry. You can convert any multimedia file from over 100 different formats. The beauty is you can convert any of your short movies or clips to whatever format you wish. They also offer a nifty little feature where you can upload files and then download them from your phone.
The only downside I have found so far is that they limit you to 150mb. To be honest that will limit you from converting movies and TV shows but I found it extremely easy to convert some of my favorite short clips to my BlackBerry without installing any software. Also they allow you to split up MP3 files to convert them into ringtones for older devices. They also have very powerful document and excel file conversions. You can convert between Access and Excel to take a document on the go or you can convert an excel file into a pdf file etc. On a side note they also let you convert compressed files from one format to another such as .rar files to .zip files. All this without having to install a thing. Check out all the different formats they can convert between at Media-Convert.com I promise you wont be disappointed.