I don't know if this would be as useful to you as it is for me, but I leaped for joy when I discovered this little Illy CS3 feature. If you deal with client-delivered vector artwork, this could make your life a ton easier. By selecting any or all of the artwork and then clicking “New Color Group” from the Swatches Palette Options, Illustrator will extract all of the colors in your selection, and add them to your swatches in a nice, neat little group! Detailed instructions below.
1. Select Some Artwork
To select all just hit Command/Control + A, or in the menu Select > All.
2. Extract Your Swatches
To do this, click on the Swatches Palette Options menu in the upper right corner, and select “New Color Group.”
You should now see your new group of swatches in your Swatches Palette, grouped together for easy reference. I have to admit that this feature would not be half as sweet as it is if they were not put into their own group. This way you can add more swatches and never lose track of your originals.