Mario_Dammann is an AppleScript for your web browser (Camino, Safari or Firefox) that copies selected text along with the URL and title into the same TextEdit file. At the end of the day, you have a collection of all your selections in one text file. Just download the script and place it in your web browser's Scripts folder.
After highlighting sections of web text, select Mario_Dammann from the Scripts menu, and the text will automatically be copied to a TextEdit file.
[robg adds: I have mirrored the source of version 0.9 onto the hints server, in case the original vanishes. I tried this, and it works as described.]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20061014070011118