Transferring large sized files from the iPhone, especially videos and movies, can be quite painful and can consume a lot of time. There are quite a few services (like YouSendIt) that help you achieve this. But if you are looking for an iPhone-specific app, TransferBigFiles is definitely a great option.
TransferBigFiles is a free to download iPhone app that lets you directly transfer photos, videos and other large files from your iPhone directly via 3G or Wi-Fi without the need to connect your device to a computer. The service also has a desktop application if you are looking for more universal access to your files.
The app may be downloaded from the App Store by clicking here. Do note that the first 100,000 users can get 5GB of cloud-storage free. Other users can transfer files up to a total size of 2GB.