I am going through all this right now. The sticky post above is great for the information. Because it is a couple of years old, I wanted to share what I have found...
Microchipping- It must be ISO 11784/11785 compatable. That means 134 KH frequency. I used "Homeagain" microchipping. I called the company and they assured me that it was compatable. Make sure the microchip number is 15 digits long. If it is 10 digits then it can only be read by USA scanners.
Worming- The worming requirment hasn't changed. It still needs to be compliant with what was said on the above sticky note link.
Forms- I called the USDA and they recommended that I bring the aphis form 7001 and the annex 2 certificate. I don't believe the EC 998 is valid after Jan 1st, 2012. These have to be certified by the USDA before we go. Here is the website newcomer link: http://www.aphis.usda.gov/animal_health/area_offices/
[nonactive] I would reccomend calling them and making sure you have everything you need to get it signed off. They told me to have the worming done before we come in. I am lucky because there is an office in town so I don't have to mail it in. If you have to mail it in, call them and get time periods as it is all very time sensitive. They told me it was $38 to certify both. Your vet must be USDA approved.
Everything else that was stated seems to be what is required now too.
Some traveling info, I am using Virgin Atlantic to ship my dog. The crate dimensions must be 2 inches larger than your pet. The smallest kennel/crate they will accept is 21x16x15. I am using "petsmate sky kennel". I got the small one off of amazon. Make sure the kennel you are using has air holes on all 4 sides. If you call Virgin Atlantic, they are very helpful and will tell you what you need. They told me it would cost $603 to ship from San Francisco to London Heathrow then another £305 once we picked her up from customs in London. I was told to call before I book my plane tickets to make sure they have room in cargo for her. You can't book them through normal flight bookings. They also said to make sure not to arrive on a bank holiday.
I hope this helps