c) Optionally: External USB optical drive, if your notebook/netbook doesn't include one. LiteOn, Samsung and others offer small, lightweight optical drives in the $50-$70 range.
7. Other data cables and stuff
a) A small four-port USB hub.
b) Optionally: phone (RJ11) cable
8. A few more power accessories
a) A three or four-port power strip, so you can share rather than hog at an airport gate or conference room. For example, Monster's Outlets-to-Go Power Strip, which has a short power cord, or their Outlets To Go 300 for Laptops. Many power strips today also include powered USB charging ports.
b) A three-to-two-prong A/C plug adapter, for when you encounter older, ungrounded outlets. (Cheap!)
c) A fresh four-pack of hi-capacity AA batteries.
d) Optional: Battery tester for AAs, AAAs and others. Five bucks at Radio Shack.
e) A six to twelve-foot extension cord
f) External hard drive.
Once you've got your travel gear together, label whatever you can, put things in pouches or baggies, don't leave them loose, and be thankful for what you don't have to schlepp.
And when you're back, reassess which things you took you don't need next time... and what you should have included.
Think I missed anything? Let me know!