There are tons of reasons to use encryption on your computers, especially if you store sensitive information on them. But I won't go into that stuff right now. I will point you to a couple of how-to pages that explain how to install and use encryption software on Ubuntu Linux systems:
- TrueCrypt With GUI On Ubuntu 7.10 is a tutorial from Howto Forge about using open source TrueCrypt disk encryption software.
- HowTo: Setup and Benchmark Encrypted Partitions in Ubuntu comes from new-ish Linux blogger Wayne Richardson, at fsckin w/ linux, and it's about more than just how to install the software--Wayne tells us about how he went about encrypting, and benchmarking, partitions. Very cool: it helps to know just how much (or actually, how little) encryption affects performance. Great work Wayne!