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Tech Stuff

Electricity

The power supply in the UK and most of Western Europe is 220-240v @ 50hz while the power supply in the US is 110-120v @ 60hz.

The US voltage is half that of the UK so appliances will draw twice as much current to produce the same power. Since the heating affect in a wire is proportional to the square of the current, you will notice that wires get hotter and need to be thicker than their UK equivalents. On the bright side, you're less likely to kill yourself! It should be noted that the little switch common in the UK to turn off power at the outlet is not common in the US, so sticking your finger in a live socket is a real possiblity.

TV, Video and DVDs

The TV standard in the UK and most of Western Europe is PAL while the TV standard in the US is NTSC. Unless you have a Multi-standard, dual voltage video player you will need a new one. It is not worth shipping televisions due to their weight and incompatibility. Tube televisions are very cheap in the USA as they are being phased out for the rollout of HDTV (in 2009). HDTV Flat screens are currently (March 2007) in the region of $1,500 and up for a decent size. Most flat screens can support NTSC or PAL playback, should you happen to have a PAL player in the US.

DVDs are generally 'region-encoded' such that a DVD you purchase in London cannot play on a DVD player that you bought in America, unless you happen to obtain (or hack) a region-free DVD player (search the net). Try http://www.videohelp.com/dvdhacks to see if you can 'hack' your DVD player to make it region free. Some computers will play both, but some also will only allow X number of times before they 'burn in' a region to the firmware of the DVD player, so say you switch from UK to US DVDs 6 times, after that, you can't make the switch anymore. Be careful.

"General Advice" Nope, generally easier and cheaper to get new when over here.

You can get power adapters, but they're not very versatile and can get warm, though for quality sound equipment it could be worth it, but for most household appliances it isn't.

Computers

Your desktop computer will probably have a switch at the rear, close to the power supply fan marked 220. If so, you can slide that over to read 110 when (and only when!) you arrive in the US. You will also need a new power cord - easily obtainable. Some will have automatically switched power supplies. These will be marked 220/110 (or 240/110) with no switch. Be careful that there is not a switch which is covered up with a sticker to stop it being accidentally moved.

If you plan to ship your computer to the US, it is a good idea to back up all your data, and take out your hard drive and carry that as hand luggage. If your desktop computer is fairly new or has a good graphics card, chances are that it is quite large and heavy, so it might also be worth removing that from the socket it is seated in and wrapping it up securely and taping it in place inside the case and pad the case as best as possible to prevent it vibrating and breaking at the connection.

All modern laptops will run on dual voltage. You may need an adapter or new power cord. You will see under the "brick" that it says 220/110 or similar. Most laptops use the standard "kettle" type mains lead which is easy to change but the more modern smaller "bricks" will need a proprietary lead.

Little Things

Hair dryers, tin openers, irons, clock radios--all of these items are easily obtainable in the US and for generally a lower price than you would pay in the UK. You will not, however, find the same selection of electric tea kettles in the US as you might in a store in the UK as they are generally not very common items in US households.

So what do I do with all this 220 UK stuff when I leave?

If you are planning on returning in a year or two, you can probably get away with placing most of your items in storage or with your folks. If this is a longer term move, you may want to consider selling them via ebay or some other method to obtain a bit of cash to bring with you to purchase new items in the US.