As a full-time event pro, I highly recommend Phottix Strato radio slaves. I bought three sets of the original Strato model about a year ago, and I'm totally sold on them. At $83 per set for the Strato and $98 per set for the Strato II, they're a bargain. The Strato has 4 channels, and the Strato II adds 4 groups as well. Unlike the new PocketWizard Mini/Flex and some other units out there, these are dumb triggers - they do not pass TTL info to the remote flash. So, the remote operates only on manual or built-in auto mode. The transmitter's hotshoe does, though, pass through the TTL signal from the camera below it to the flash on top of it. So the on-camera flash can still operate TTL. And, a remote flash can be awakened from sleep. I've used mine up to 150' apart in large event halls. In a year of regular use, mine have never misfired or failed to fire.
Here's what I like
1. They're cheap.
2. They're compact.
3. They take AAA batteries.
4. They feel well-made.
5. The transmitter has a metal foot.
6. The transmitter and receiver both have a hotshoe on top.
7. The on-camera flash (on the transmitter) can still operate TTL.
8. The remote flash can be remotely awakened from sleep.
9. They can trigger 1 of 4 channels, or all 4 at once.
10. Good range.
11. Great reliability.
I bought mine direct from Phottix' online store. In the US, they're also available from Adorama in New York.
'No matter where you go, there you are.'