Well... now the iPhone is out. I've played with it and it's slick. In traditional Apple fashion it's has a user interface that's a joy to use. It's also a bit expensive and I have at least a year left on my current T-mobile contract. It's also a closed interface that you can't really expand or add anything to unless you hack it and then you've got to deal with Apple "fixing" it on each new release and then you have to wait for someone to figure out how to break it again.
I also considered the new iPod Touch. It's an iPhone without the phone but it still has WiFi capabilities. However you're still in the same boat as you are with the iPhone when it comes you doing your own thing with it.
So I looked around and ended up getting a Nokia N800. The N770 had been taunting me on and off for a while with low low pricetags so when the N800 dropped to $230 or so I snapped one up.
It's a slick little device. Not as small as something like an iPhone/Touch but definitely more more portable than a lappy. It runs linux and is pretty quick. There's all sorts of ongoing development going on for it through the Maemo development environment. It's a snap to jump on a WiFi network, browse the web, watch a YouTube video, stream from Shoutcast etc. I've already had to figure out how to install ntpdate, get root access and set the clock on it. I guess that part of it appeals the my inner-geek. The new 2008 OS is out any day now... so this should hold me for a while.