Not sure how many people are using it, but google browser sync has been around for a while, and I've kind of ignored it up until now.

As hinted at in other posts here, I've been messing around re-formatting and testing other OS's for a while now, and while I don't really care to sync work->home computers, or even laptop->desktop, it *is* useful for keeping a backup of your data. When I'd previously had to reset every piece of data in firefox, it's just a simple matter now of sync'ing after the re-install and everythings there (bookmarks, cookies, etc).

While on the subject of being a google fan boy....

I was always a bit so-so about RSS readers, but google reader is truely awesome, it's probably one of the nicest 'web interfaces' I use day to day (in terms of functionality). Very handy for keeping track of sites which don't update so often, and the brilliant part is that you can access it anywhere and keep track of what you've read.

Lastly, google webmaster tools is a not all the widely advertised but extremely useful tool for website owners. Originally was part of google sitemaps, but it has been expanded to provide extremely good data on which pages have been indexed and search terms.