I love showreels in general, though they tend not to tell a story in the same way as a trailer, they still use the principle of packing all the coolest bits on hand into the shortest time and (if done well) adding their own feel on top.
There is a new showreel from SOFTIMAGE|XSI on their site which includes some great projects (plenty of which I thought were all Maya - but obviously some bits XSI was used). I quite like some of the japanesiness of the showreel - some great stuff to behold anyhow.
SOFTIMAGE Youtube Channel
The next way to experience the wealth of wonders that XSI technology and sme awesome artists can bring is via the new SOFTIMAGE Youtube channel.
This is the Showreel in its lower res Youtubiness:
Other vids worth checking out include The Final Fantasy XI - Opening,
Solar, Short Film and many more.