I've been using Ubuntu for a while, and when I use Firefox, Google has auto-complete by default. I don't know where it comes from FF or Ubuntu or Google.

Google Suggest, Firefox add-on, will do that. Perhaps that's what you have?

It comes with Firefox 2 by default (no add-ons needed).

It was added last Tuesday to the experiments list.

blogoscoped.com/forum/115642.h ...

> It was added last Tuesday to the experiments list.

Ah, so that's where Ionut spotted it (?) :)
I updated the post.

Yeah, I noticed sometime last week.

I'm guessing this doesn't work with iGoogle? I can get it to work when I go back to the classic homepage, but not on iGoogle, which is unfortunate since it's a pretty handy feature.

I think Google should refer to this experimental search on its homepage.
Don't you think?

That's nice! Now I left Left-hand search navigation and moved to Keyword suggestions