Here are a few of the topics that come up again and again in the UK VJ Forum. This info is subject to change, please feel free to update/correct/append as you wish.
On Topic - The Visa Stuff
Direct Consular Filing in London
If the US Citizen and their spouse are living in the UK, you can probably file directly to the embassy. See more: DCF London
K-1 and CR-1 In The UK
Embassy Stage for All Family Visas In London
Beyond the Visa!
The first piece of off topic info you need is this thread. Come over and say hi!
Shipping - For a general guide to shipping your stuff.
Living in the US
UK Foods and where to get them (and Pubs!)
(Sub-Section: On the substandard quality of US bread, bacon and cheese)
How to watch your favourite sports/TV shows in the US