Unfortunately, Agra is the home of the tout. Agra may well be the world's biggest tourist trap. An entire city focused on fleecing tourists. When I jumped in my cab for the day, the driver came with an "assistant". Nominally a free tour guide, his basic purpose was to get me to as many commissionable shops as possible. Should have left him at the train station.
Security at the Taj Mahal is tight. You can bring virtually nothing inside the security barriers. They have a somewhat sketchy locker system outside. I suspected I was being made victim of a classic scam: guide assists with the locker, leading tourist to a specific one. He leaves his cellphone (probably stolen from yesterday's mark) in the locker as security. Tourist enters site, returns an hour or two later to find both stuff and tour guide gone forever thanks to a duplicate key. And I had some pretty good stuff in my bag (MP3 player, blackberry). Realizing the scam after 10 minutes or so (or maybe just paranoid), I feigned illness (no reentry normally allowed) and convinced the guard I needed to get medicine from my bag. I then switched to a locker which only I knew. The "guide" was quite surprised when he discovered my switch.
The Taj Mahal was a bit of a disappointment, having been to Humayun's tomb in New Delhi the day before. Humayun's tomb was the immediate predecessor to the Taj and is located as the main attraction in a park filled with tombs of various types. Not quite as beautiful, not quite as big. But very few visitors and you can wander around virtually anywhere. After that, the Taj was good but didn't "wow" me with its size or scope.
Fatehpur Sikri is located 40km outside of town (thus, another $10 or so on your cab for the day -- I love India). A fascinating historical site -- I thought the best part was the separate palaces for the emperor's Hindu, Muslim, and Christian wives. Pretty good tourist scam going (I was warned by my driver) -- they have a guide cartel ($3 or so). This isn't necessarily a bad thing since you need a guide, and this ensures some degree of reliability. However, near the end of the tour they vector you out the back of the mosque to a handful of street vendors who are supposedly the descendants of a prophet's family. They sell pretty nice marblework (especially the elephants carved inside elephants) supposedly carved by grandpa. This is effective because you don't normally see this type of item in Delhi/Agra so it appears unusual. However, go to Mahabalipuram (a hotbed of marble carving) and every vendor on the street is selling exactly the same thing. A good example of geographic arbitrage.
The tourist train (Shatabdi Express) to Agra is fast, cheaper than a car, and filled with other tourists. I never figured out how to buy a ticket Indian-style (50+ windows for different trains and types of fares), but they have a nice tourist ticket office where they speak english and insist on foreign currency. However, have written down exactly what train #s you want from the internet since they don't have any train schedules there. The one or two people in the room who had brought one were extremely popular. Next time, I would have prepurchased train tickets online and had them delivered to the hotel.
And finally, beware as a tourist. I was told the restaurant I wanted to eat at was "closed". Of course, it had been open earlier in the day when we drove by on the way to something else. Others were 10 miles or more away (when the map showed 2). The restaurant my driver attempted to take me to was absolutely empty at 6:30 at night. Fearing poisoning (which unfortunately appears a regular problem -- then they can get a commission from the doctor), I left immediately. Zorba the Buddha, however, was excellent.