If you just want to play your multimedia files, gmerlin will do the job with an incredibly simple GUI. It has a playlist and many other features you might want to have (fullscreen video, CDDB, seek slider etc).
Music fans can rip audio CDs or record their analog sources with their OSS soundcard and use gmerlins audio encoders to make Ogg Vorbis files or Mp3s. Computer artists can create freaky animations with blender and use gmerlins singlepicture plugin to make quicktime movies (with alpha channel), which can be read by broadcast2000 for further editing.
If you are a C++ programmer, you can study gmerlins sourcecode and use it under the terms of the GPL. If you want to become a famous C++ programmer, you can contribute something or become the maintainer of a subproject.
Are you sick and tired of installing commercial media players after clicking away a 10 page license, which focusses on keeping the companies power? Did you already learn, that your "free player" is actually a feature limited demo version of another program, which can be downloaded after paying $ 29.99? Gmerlin comes to you absolutely free with all features and plugins we were able to program. Gmerlin comes in one single tarball, which contains all 3rd party libraries which are necessary for playing all the stuff. This eliminates the need for asking search engines, where to get libXXX-YYY and avoids version conflicts between player and library versions which cause a large percentage of the bugreports of other players.
Sure, gmerlin it a huge package and it takes damn long to compile. But once you have installed it, you won't need much more for universal multimedia support on your PC. Sure, gmerlin can't play some things, which are already supported by other opensource players. This is due to the fact, that gmerlin is a rather young project (started in November 2000) and it's not completely finished yet. Check the TODO list if you are curious about the things which will appear in future versions.