VLC is basically a universal, free and open source media player that's been available for computer based platforms for quite some time now and it's become very popular since it's a single install to play almost every single media format available. For the mobile platforms (e.g. Apple 'i' products), we've had to contend to specific file formats so if you want to watch a video, music or whatever that isn't supported on the platform, it had to be converted into a specific file format that the phones/software will accept.
Well not any longer. Just a couple of months ago the company Applidium released a version of VLC Media Player to the Apple iPad and now they've released it on the iPhone too. Only works if you've got a iPhone 3GS or an iPhone 4 otherwise also works with 3rd and 4th generation iPods.
Once you have installed the app, all you have to do is connect your iPhone to iTunes and add VLC to the File Sharing list. It will then prompt you to select the file you wish to copy to your phone.
Never again will you have to do those tedious and time consuming conversions any longer.