Just a quick note - it might be slightly trickier if you're running 64-bit Ubuntu. I've had quite a few woes of my own with 64-bit Flash and Linux. At present, Adobe's 64-bit native plugin is working fine for me on my desktop (a Phenom II X4) but their badly configured compiler settings resulted in a few nice Firefox crashes before I actually disassembled the thing and found out that the Athlon 64 chip in the kitchen computer wasn't supporting a few SSE2 instructions that the plugin used despite supposedly including SSE2. I had a lot of crashes with the nspluginwrapper setup installable via Apt too. It only worked for me when I manually built nspluginwrapper and installed 32-bit Flash myself.
If you're on 32-bit Ubuntu or nspluginwrapper hasn't crashed Firefox yet, then smile and disregard this, because you've dodged the hell on earth that is Flash on Linux.
--Danny :ninja: