across the ones you've already bookmarked? Google can do it by
searching only sites in your Google bookmarks. Unfortunately, I don't
use Google bookmarks, as all my bookmarking is done in del.icio.us.
You can do it by going to this site that has a script which uploads
your del.icio.us bookmarks and puts it in Google.
Warning though: you will have to log in with your del.icio.us login. To be safe, just change your password before using this utility, then change it back to the original once the import process has finished.