I've been a user of Konfabulator, now Yahoo! Widgets, since day one. I love it. Apple has now given us their Widgets in Dashboard. I love Dashboard, too, but one thing that has always bugged me is that the Dashboard background is too transparent for my liking -- I want to see less of the background.
What I just discovered is that if you set both Yahoo! Widgets and Dashboard to use the same F-key for activation, Dashboard then 'uses' the Yahoo! Widgets background (a barely-transparent dark blueish color). If you don't want any Yahoo! Widgets to show, just have it open with no widgets open. Not a big deal, but it made Dashboard more usable for me.
[robg adds: This worked as described, though I sometimes had to cycle through the 'deactivation' keystroke a couple of times to get rid of both the Dashboard and Yahoo! Widgets. Since I also would prefer a less-transparent background, I spent a bit of time in the Dock package, searching for a background image that might be being loaded, but without luck. I also dug around with defaults read, looking for a transparency setting, but also came up blank. I imagine the Dashboard is just setting a transparency level directly in the code, which means this workaround might be the only solution.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20060124151128326