Here's what's on our list (what we've done, and what we've got to do), as we're going through this right now! Would love to hear other ideas, too!
1. Schedule Garage Sale or Donation Pick Up (even if you're storing or moving stuff, you'll still probably have stuff to sell of give away - we're getting rid of EVERYTHING, so we had 2 garage sales AND a Salvation Army pick up)
2. Get reference letters from Landlord, Employers (not sure if this is really necessary, but we figured they might come in handy when looking for a new flat, etc.)
3. Cancel all services, utilities, etc.
4. Closed all bank accounts except for one (my husband and I still had several separate accounts from before we were married and consolidating them will make it easier, I think, to transfer our money, possibly?)
5. Go to our dentists, doctors, etc. (I guess I won't get health benefits my first 5 years in the UK, so I'm trying to get as checked up as I can, while I still have insurance)
6. As others said, gather all important documents, and update anything as needed (for example, my passport was due to expire in 1 year--I'm not sure if I could have applied for a visa on that, but I just went ahead and got a new one anyway)
7. Buy a few things we'll need in winter in the UK (that we didn't ever need in Texas) - wool socks, a nice heavy coat, a pair of boots, etc. I'm sure I'll need some of that right when I arrive, and I'd rather make those purchases while I have time and I'm paying $ instead of £