Not any adds either in magazines or out on town here in Stockholm/ Sweden, at least I have not seen em compared to other brands.
But there have been quite a few phoneshops i've been asked to show them the phone (pre-release N900 and later on retail version)

So I guess the N900 must be the most "secret" phone ever by Nokia.
Still not seen any device In a phoneshop and they still repeat the same old "it will be in stock soon"

Guess that will be Meego devices with the current delivery speed over here.

Here in Denmark, I haven't seen any N900 commercials or anything.

I've seen the CPW adverts here in UK, vodafone stocking it, and posters.

To some extent the UK mobile market is probably the most competitive/innovative outside the far east, so maybe the higher UK focus is intentional?

Not advertised in the United States (at least the Washington D.C. area as far as I can tell).

why would they advertise? this is a geek's phone and geeks dont need advertising, it spreads via forums and the web

the average user wont like this phone, thats not their target, so why waste money

I've seen posters on billboards on the North Circular and also on the M4 to Wales. Lots of posters in Carphone Warehouses as well. Seems a lot more visible than Nokia phones usually are... I've also seen Sony and Blackberry adverts. I think Blackberry "sponsor" film ad breaks on one channel and were sponsoring True Blood episodes (only saw one or two, so not sure if that continued).

Also, I keep seeing lots of web ads on lots of sites... things like football (to you north Americans, sawkah) sites I look at on the Times, Guadrian and telegraph websites advertise it and I think at least one of them has a review on their site as well.