Safari 3 included a hidden circular page loading indicator. While the preference for that circular indicator has vanished in Safari 4, you can actually get it back by setting some of the hidden Safari 4 preferences in the correct fashion.
To get the circular progress indicator back, you need to set the DebugSafari4IncludeToolbarRedesign preference to FALSE, and leave (or reset) the DebugSafari4LoadProgressStyle preference to TRUE (its default setting). So if you haven't modified either of these settings yet, you just need to do this in Terminal:
defaults write com.apple.Safari DebugSafari4IncludeToolbarRedesign -bool FALSE
If you've previously modified the other preference, you'll need to set it back to TRUE:
defaults write com.apple.Safari DebugSafari4LoadProgressStyle -bool TRUE
With the prefs set in this combination, you'll get a pie chart on top of the favicon that fills in while a page is loading. (I originally wrote about this on my blog, if you want or need more details.)
Mac OS X Hints
http://hints.macworld.com/article.php?story=20090226073915279