If you have enabled your dock to be moved to corners and sides (see Move and corner your dock), one of the small annoyances is that the pinning and orientation revert to bottom middle after a logout or restart.
I noticed this morning that Frank Vercruesse has released DockLock 1.0, which exists solely to restore your preferred dock pinning and orientation settings automatically.
Until Apple decides whether to officially support pinning and orientation, this seems like the best solution for those that prefer their dock in positions other than bottom middle. I tested it, and it does exactly what it claims to do.
Mac OS X Hints
http://hints.macworld.com/article.php?story=2001070109400687