I'll add one more thumbs up post here. The N900 is essentially the last of Nokia's "Internet Tablet" lineup (the N9 has more up to date hardware, but sacrifices a lot of the features of the N900), and as such, is pretty much the only general-purpose computer in a cell phone form factor even today.

Every device released in the last couple of years has been, in my opinion, either an iPhone or an iPhone clone -- beautiful to look at, but designed with innumerable walls stopping you from performing any "unauthorized" activities. The N900 is truly open; not only can you customize the look and feel, you are given access to every feature of the device. Full access to the file system! No limits on adding your own software. No limits on removing or replacing software either. Heck, replace the kernel itself!

Nobody makes devices like the N900 any more...