Texas Tax Back offers foreign shoppers to get back local sales tax. You'll need to do this at their office in the Galleria Mall in downtown Houston. Bring along the merchandise, receipts, passport, and travel details and they'll process the refund to your credit card. Only receipts with a sales tax of over $10 are valid (although you can combine receipts for the same store to get past this limit) and you must pay with a credit card registered to your name. The rate at present is 8% so if you have stocked up on presents the savings can be sizeable. There are also two offices in San Antonio.
Despite a change in regulation which technically brought the end of tax-free shopping at UK airports for persons travelling within the EU, electronics chain Dixons continues to offer tax-free prices to all travellers, regardless of their destination. The Dixons Tax Free shops are a great way to pick up a bargain (saving 17.5%) without having to worry about different power suppliers, warranty and import duty issues that may be associated with buying abroad.
Whilst the range is limited, they do offer a number of key brands including Apple iPods and major electronic brands. Large items can even be delivered to your home address or picked up on your return. Pre-ordering is available by phone and details of products can be found on their website - www.dixonstaxfree.co.uk.
I would recommend that you pre-order or check availability before you fly. It saves a lot of time and they can get stock in from different terminals if required.