Shockingly, this stuff doesn’t take up as much space as you might think. The SLR is ALWAYS with me. We never carry the hard drive and the laptop in the same bag so that if one is stolen, we at least still have the other (both have all our photos on them).
Acer Aspire One Netbook
2 ipods
2 Kindles
Headphone splitter (for watching movies on laptop. A must have!)
Canon EOS Rebel T2i with 18-135mm Zoom Lens
Joby GP3 GorillaPod SLR-Zoom Flexible Tripod + BH1 Ball Head with Bubble Level
Seagate FreeAgent GoFlex 1.5 TB USB External Hard Drive
Power converter plug kit
One of the plugs that turns one outlet into 3 outlets. We bought this super cheap at a hardware store and it is fantastic for allowing us to charge multiple things at once.
Phone (no phone plan, more for alarm/GPS/wifi use)
Chargers and cords for everything. We also brought a short ethernet cable, just in case. It has come in handy a few times when a hostel has internet, but no wifi. We can then plug in our own computer and not worry about keystroke loggers etc. All the chargers and converters go into a stuff sack so we hopefully don’t lose them.
USB thumb drive – this has come in handy when we need to print something. We save it onto the thumb drive and take it somewhere to be printed.
The Parallel Life 
What is the size of your back up USB mini-hard drive and also the thumb drive? Would be interested to see how much space you brought for a trip around the world. Also, do you upload all your photos to a service like Flickr or Picasa as a third back up or to make blogging easier?
Our thumb drive is old, it’s just 1G, but we use it mostly when we need to print something out, we can put the file on that drive and take it somewhere to print. The back-up hard drive is either 1, or 1.5 T, which I think will be plenty big enough. They are getting bigger all the time, so it wouldn’t surprise me if within a few months you could get a 3 T one for the same price as we got ours. We do try to upload some of our pictures to Flickr, but it takes forever and requires a really good internet connection, so we haven’t gotten everything up there yet. we’ve considered making CDs at some point and sending them back home, but that just seems like a huge process. At this point we keep all the photos on both the laptop and the hard drive, and then they are in different bags when we travel in case something gets stolen.