KMPlayer, a simple frontend for MPlayer.
It can play DVD/VCD movies and from file or url. 
If setup right, KMPlayer can embed inside konqueror. Which means if you click
on a movie file, the movie is played inside konqueror.
It can also embed inside khtml, enabling movie playback inside a html page.

KMPlayer needs KDE3.1 and a working mplayer somewhere in you PATH.

Quickly installing MPlayer
Download the sources from http://www.mplayerhq.hu/homepage/.
If you want quicktime support, also download the quicktime dll's
(http://www.mplayerhq.hu/MPlayer/releases/codecs/qt6dlls.tar.bz2) and unpack
them and copy the files to /usr/lib/win32 (make this dir if it doesn't exist).
Untar the mplayer source package (tar xfj MPlayer-0.90rc3.tar.bz2), change to
that directory. Make sure $KDEDIR/bin is in you path (check if you can run
'artsplay').
Now run configure (./configure) and make ('make'). Install it as root ('su -c "make install"').
Finally you must setup the config files in ~/.mplayer ('mkdir ~/.mplayer').
Copy the files, from the mplayer sources, etc/codecs.conf and etc/example.conf as codecs.conf and config resp 
('cp etc/codecs.conf ~/.mplayer; cp etc/example.conf ~/.mplayer/config').
Next change ~/.mplayer/config with an editor and change the video driver (vo=xv) and audio driver (ao=arts) and remove the last line.

Quickly installing KMPlayer
Untar the source package, run './configure' and 'make'. Install as root 'su -c "make install"'.

KMPlayer doesn't work with all the video drivers that mplayer supports. 
I tested only xv (X Video Extension) and x11 (Image/Shm). If none work, you 
might try the patch for the x11 driver and see if that works for you.
You might need to change mimetype settings (Control Center | KDE Components | File Associations) to make sure KMPlayer (or 'Embedded MPlayer for KDE' in embedded tab) is set for all the formats you want to play with KMPlayer.
Also make sure in the 'Embedding' tab 'Show file in embedded viewer' is set.

Enjoy!