Finder windows..
Command + click the pill button in the upper right to cycle through toolbar apearances.
Command + Option + Click the pill button to open the customize tool bar window.
Control + click the tool bar for a list of options.
Command + Option + click + drag any application to place it in the tool bar
Column view: Option + Click + Drag the column arrows to adjust all column widths at the same time.
List View or Icon View: Command + Option + Click + Drag to move the window contents around without resizing or actually moving the window itself
Option + Click scroll arrows to jump by pages rather then smooth scrolling (this works in many applications)
Holding down the Command key while moving a file from one drive to another will move the file and delete the original rather than copy the file.
Finder menus (and in some applications)
Hold the option key down after you click a menu, you'll see some items change. Show Inspector int eh file menu can be real useful when getting info on many files, it emulates 10.1 get info in that the wondow cycles the items you select instead of needing to open a new window with each item.
Dock...
To stop dock items from moving around when your'e trying to drop something on them hold command + option while you drag a file to the item
Command + click a dock icon to revael it's location in the finder.
Command + Option + click a dock icon to hide all other application except that one
Control + Option will change the pop up menu to include "Force Quit" instead of "Quit" and "hide Others" instead of "Hide" (The control key isn't really needed but it will make the menus pop up faster than simply clicking and holding on the dock icon) In teh case of the Finder icon, it allows you to relaunch the Finder from the Dock.
I had serious (very serious) video issues with 10.3. at first. i last my dual display and had trouble even getting a single display to act properly. Thanks to a link in the Apple forums to a retailer I was able to swap a file for my GeForce 4MX card and get all video support back. I am quite amazed at the fact that the file and fix came from a retailer and not from Apple or nVIDIA. But oh, well, the issue is fixed. Anyone else notice that applications (especially web apps) crash quite a bit more than they used to? I've submitted at least 5 bug reports to Apple today alone. Everyone should put "Apple Beta Tester" on their resume.