I've always been a fan of the Apple iPod. My first one was the second generation and it had 20Gb of storage space. I used it as much as a music player as I did a portable firewire hard drive.
How things have moved on! The latest models go up to 160Gb! However, the one that caught my eye was the iPod Touch. Not so much a music player, but a portable computer. The version I have is the 32Gb version and I have my music on there as well as a few videos.
However, the thing I use it most for is presentation of work. It can can handle pictures which can be seen as a slideshow or manually flicked through. More importantly for me, it can show audio visual slideshows which are in Quicktime format. I can now carry all my photo essays in my pocket!
Its next amazing ability is its full web browser. Now, our mobile phones can browse the web, but the Touch (like the iPhone) has a full version of Safari, which means you can see web sites in their fullest and not a cut down version that mobile phones show. Also, by turning the Touch on its side, you can view the site horizontally. The only downside is that the Touch doesn't yet support Flash, but I'm hopeful that this will be addressed.
I use this a lot to do research when on the road and working on a story. It also has a brilliant email application (called Mail) which lets you download email and reply, much like you would from a laptop. The thing that puts it head and shoulders above mobile phones though is that it can open attachments properly and without fuss.
To add to its usability, if your mobile phone supports it, you can install Joikuspot. This turns supported mobiles in hotspots, which means if there's no WiFi for you to hook up to with your iPod Touch, you just start the software on your phone, and look for it as a WiFi hotspot on the Touch. Naturally this will also work with a laptop.
If and when Apple bring out a new 3G iPhone (rumoured to be June), this will naturally eliminate having to set up your Joikuspot hotspot.