For flashes, I think I'm starting off with the 430EXII. I think the 270EX would be nice, but the lack of IR reduces it's usefulness for off-camera shooting.
The 580EX is nice, but for me, it's probably overkill.
Why would it be? I read countless reviews where the reviewer say eventhough 430 EX II is a very capable flashgun, he/she regretted not spending extra to get 580 EXII cause the extra features that is found in it is proved to be very useful indeed and now he/she need to shop for a 580 EXII. I'm aiming for a 580EXII straight away so that if I ever need to make a wireless flash system, I can borrow my friends flash gun and do not need to be surprised with the control cause I will be using the flash gun I'm used with as my master.