Ok, so maybe some of you might think that Babelfish's the best translator out there. I don't know about that , but I do know where my towel is ;)
So, boys and girls, here's the bookmarklet that allows to translate your current web-page using the babelfish translation engine.

javascript:location.href='http://babelfish.altavista.com/babelfish/tr?trurl='+encodeURIComponent(location.href)+'&lp=%s&btnTrUrl=Translate'

To make it useful, save it as a bookmark in FF (or as a new search engine in Opera) and give it a keyword/shortcut by editing the bookmark's properties in FF (or the search properties in Opera). Let's call him, say 'bf', that should do it.

Here are some examples:

bf en_fr
bf fr_en
bf en_ja

Enjoy!
G.R.

Here's perhaps the most powerful bookmarklet I've ever created ...
This one translates the current web page from your current browser session into another language!

Syntax from the address bar in your FF or Opera browser:

 tr <FROM>|<TO>

Examples:

 tr en|de
 tr en|fr
 tr en|pt
 tr de|en

Here's the bookmarklet code

javascript:location.href='http://translate.google.com/translate?u='+encodeURIComponent(location.href)+'&langpair=%s&hl=EN&ie=UTF-8&oe=UTF-8&prev=%2Flanguage_tools'

FF instructions:
Copy/paste the code in a new bookmark. Then, in the new bookmark properties, edit the keyword/shortcut field and insert 'tr'. That's it!

Opera instructions:
Copy the bookmarklet code. Then, in tools-->preferences-->search-->add-->details, paste the code in the address field, fill in a name for in the name field, and write 'tr' in the keyword field. Then save all. That's it!