Did you want to remove traces of surfing activity from an internet PC, or did you want to wipe a drive COMPLETELY so that the data can't be recovered?
For wiping data completely from hard drives,
Eraser can't be beat. It's free software, but you can donate to them if you find it useful. Secure data deletion really rocks.
For removing traces of internet surfing activity from PCs, I prefer
Window Washer. This one costs money, but is worth it if you need to clean up a machine. Pretty thorough.
Of course, if you were using the FireFox web browser (v1.5 and up), you could always just go Tools >> Clear Private Data to erase all the personal information stored during web surfing.