Hi - I'm Gavin's (Bungle's) wife - since he's leaving early so that he doesn't have to deal with the actual logistics of moving he asked me to respond.
You have two options - by weight or volume.
Weight
A lot of people mention USPS, but they cost about $3.45/lb for surface packages.
http://ircalc.usps.gov/default.asp?Mode=...&CID=10142
UPS has the best per pound rates - $3.24/lb. And that is for 5 day delivery (much better that surface post).
http://wwwapps.ups.com/calTimeCost?loc=e...svl=SubNav
FedEx has higher rates; around $3.90 I think. But it is essentially the same service as the UPS above.
http://www.fedex.com/ratefinder/home?cc=...Rates+Corp
M-Bags - If you have books to ship you can get an M-bag from the US post office and ship up to 66 lbs of books to one address. It only costs $0.95/lb. It is a surface service so it takes 6-8 weeks. Apparently most people have been successful in packaging their books in boxes, then putting them in the M-bags. But some postal employees won't let you do that and will insist they go in loose. Check with your post office if you want to use M-bags and don't ship books if they won't let you box them (unless you don't mind damage or loss). Also, you need to line your boxes with garbage bags to protect from water damage. But for $0.95/lb you can't go too wrong. You get the M-bags from the post office. They are free, but you are supposed to return them and some post offices will need to order them for you.
http://ircalc.usps.gov/default.asp?mode=...ript=false
Volume
You need to buy a minimum of 200 cubic feet usually. You could also get a whole or half container (40 ft in length and 2000 cubic feet or 20 ft and 1000 cubic feet respectively). I have seen that people on the American expats site paid about $5000 for a 20 ft container.
I received a quote from Omega to ship 200 cubic feet for $7.90/cuft. It came out to around $1700, including documentation. This is a door-to-door service, so they actually come in and pack everything up, fill out the customs paperwork, and load the van. They also unpack on the other end. The price doesn't include extra charges for boxes, packing fragile items (china), fuel surcharge, insurance, or security fee for the shipper on the UK end. Someone on the American expats site used Omega and paid about $300 for those extra charges.
http://www.omegashipping.com/
http://www.stevensworldwide.com/
There are also some places that will palletize smaller shipments for you, but I've heard that you can have problems getting through customs with those types of shipments. And they are port-to-port. I got a quote for $1150 from Upackweship.com for one full pallet + palletizing fee from NYC to London.
Check out this site too:
http://www.movingscam.com . They have a bulletin board with moving company feedback, including an international section. They recommend getting three quotes and using companies that will offer to do a walk through of your house to give you a better estimate.