I went through this decision a couple weeks ago and chose a 430 EX II. I was looking for a versatile flash to be used as a dedicated unit and off camera. I was considering some Yongnuo's as well (primarily the manual 460II and 560). My reasoning for choosing the 430 was because I just trust Canon more. I really like the idea of an inexpensive flash with similar (if not better) features, but don't want to worry about any potential complications which have arisen with Yongnuos. There are, however, many many people whom are perfectly happy with their Yongnuos, so I certainly won't knock that as I don't have any first hand experience.
If the Yongnuo route is one you are considering, then check out the YN-565 EX (similar to Canon 580 EX II), or the YN 468 II (Similar to Canon 430 EX II). Those are both ETTL capable. From what I've heard reputable sources are the following:
Amazon Cheaplights
ThePhotoGadget
- One year store warranty?
Yongnuo's eBay
- 1 year manufacturers warranty
Otherwise, I'd say the 430 EX II is a great choice in the price range. Primary fall backs for it would be no PC connection and you're not able to use an external power supply (which could speed up recycling for sports shooting).
As far as off camera flash is concerned I went with the inexpensive Cowboy Studios NPT-04 trigger which has been working flawlessly thus far. Yonguo makes something similar (RF-603) and another common one would be the Cactus V4 or V5. These are manual radio triggers which allow for off camera flash, but you cannot control the flash from the camera. More expensive versions would be Pocket Wizards, Cybersyncs, Phottix, Skyports, Pixel Knight or Kings, Radiopoppers, etc...The more expensive ones generally have options to buy transmitter/receiver which allow for TTL as well. You can also consider a TTL cord of varying lengths.
Hope this helps and wasn't too jumbled.
Edit: I don't believe Yongnuo flashes support HSS or 2nd curtain sync?