Some time back I had an abortive go at making a bookmarklet to do various things with Google Translate that weren't that straightforward. It all went a bit off the boil but thankfully it's pretty irrelevant now that Google's done what was needed all along and given us a dead easy widget to drop into your site and do good-enough translations on-the-fly. Links on the page are also appended with parameters so that it will translate subsequent pages too, as long as the widget is on them. Nice.
Actually I'd still like a bookmarklet (not G Toolbar) that lets me highlight a bit of text and translate to/from a language of my choice. Got a bit stuck with the whole IE prompt thing but hey, perhaps I'll have another go.