Are there any apps that convert files for iPhone 3G? So I have an iPhone 3G, and it can no longer be updated to the newer versions of software. So, I was just wondering if there were any apps that would be compatible with my phone to convert files and movies so I can watch/view them on my phone.

PLEASE HELP :)
iTunes can convert movies into an iPhone friendly format. If you have more specific needs, Handbrake is the video converter of choise on OSX.

For other files, applications like GoodReader or Air Sharing (link to iPhone version, there is also an universal version available) allow reading most "standard" document formats and also offer ways to upload files to your phone without using iTunes.