MPEG4IP is the master project which originally contains mp4creator. Unfortunately the development has stopped as of 9/28/07. MPEG4IP provides an end-to-end system to explore streaming multimedia. The package includes many existing open source packages and the "glue" to integrate them together. This is a tool for streaming video and audio that is standards-oriented and free from proprietary protocols and extensions.
MP4Muxer is the GUI frontend of mp4creator. It provides easy and fast access to mp4creator's complex command line options. Both tools are designed to work seamlessly and fully integrated.
x264 is a free library for encoding H264/AVC video streams. Unofficial builds for Windows are available from Jarod or Sharktooth. x264 has won awards for its exceptional encoding quality and speed. There are many tools, that are using x264, including ffdshow, VLC, ffmpeg, Handbrake and MeGUI.
QuickTime is a free MPEG-4 AVC player. It is user friendly and can handle AVC high profile since version 7.6. It needs however a fast machine. The Pro version ($20) can even reencode and cut videos using the time slider.
Finally something to play with. Apple has dozens of DRM-free HD clips for download, including music videos from Jonas Brothers, Miley Cyrus, Underoath, Steve Miller Band, David Gilmour, Blue Man Group, Rufus Wainwright, Pat Metheny Group, Nine Inch Nails. They have also travel, science and nature clips from IMAX, BBC and NASA.