I had to post a couple of photos of this! The SanDisk Extreme Portable SSD. I actually wrote about it a while back when it was first announced, but I just got my hands on one today and it was even smaller than I though it would be!
It comes in 256GB, 500GB, 1TB and 2TB variations at the moment, and the smallest of those sizes is under $100 which is pretty amazing for an SSD. Now that these drives can use mSATA drives in them, they have taken a real fall in price in the last year.
SSDs like this are roughly four times faster than a typical portable hard drive, and this SanDisk Extreme Portable SSD should be able to reach 550mb/s.
These things are pretty exciting because it can really lighten your load when travelling, and allow you to easily carry a copy of your photos from a trip right there in your pocket. I can actually fit this thing in my wallet!