You need to use USB Repeater cables. The cables have active boxes on one end that extends the signal. I use 16ft USB Repeater cables; in theory you should be able to daisy-chain five of these and still have a strong signal. I very rarely need to use more than two on a port.
Here's what I use:
GWC 16.4 ft. USB 2.0 Repeater Cable Model AR2500- 5MAs for ports, make sure you have an adequate number of USB
controllers. This is different from the number of physical USB ports you have on your computer, as multiple ports may share a single controller. To check the number of controllers you have available, you will need to check Device Manager (I think there's info somewhere else in these forums or maybe in the wiki about how to do this.) Each controller should be able to handle data streams from two PS3 Eye cameras at full res and 60fps.
If you're not getting that rate, then there is a bottleneck somewhere; either you have too many cameras using a single controller, your computer is not fast enough, or your storage device is too slow. (Or a combination of these.)
Hope this helps.
Greenlaw
Edit 1: Sorry for the bad link. Fixed it.
Edit 2: Also, you can use a hub but bear in mind that you're still limited to two camera per controller. In other words, you can't plug more than two cameras into a hub, and if the controller has a camera connected in another USB port it owns, then you can only connect one camera to that hub.
Edit 3: As for knowing which ports are owned by which controllers, I don't know how to determine that. I've always just figured this out by trial and error. If somebody has a better method (a software utility that tells you,) please share you knowledge. Thanks in advance!