Thunderbolt connections

Can the thunderbolt connections on my iMac be used for any devices that normally use a USB lead?...with suitable adapters. (I don't want to connect other monitors or pc's)

I've got a camera, cddrive, 2 Garmins, 2 iPods 2backup drives and USB pen drives all wanting to use the 4 usb ports. It would be useful if the Thunderbolt ports could be used as well.
4 USB ports is seriously inadequate!

No, the Thunderbolt ports are backward compatible with MiniDisplayPort but not USB. Amazon sells some very nicely designed USB 2 and 3 port add ons that match the decor of the iMac and work very well giving extra ports. Keep in mind that if you need those extra ports to power hard drives or recharge your iPad, then you will need a powered hub.

Actually, Thunderbolt ports CAN be used as USB ports:

Amazon.com: FosPower [3*USB 3.0 + 1*Gigabit Ethernet Adapter] 3-Port Superspeed USB 3.0 Powered HUB to RJ45 10/100/1000 Gigabit Ethernet LAN Wired Network Adapter Converter for Laptops, Ultrabooks, Tablet PCs with USB Port (Windows XP/7/8, Mac OS-X,

Part of the reason Thunderbolt is so awesome is that it can be adapted to be almost ANYTHING (including FireWire!). However, the cheaper and better solution is exactly what Charlie mentioned ... a powered USB hub. Takes up one of your USB ports, turns it into four or more depending on what you buy. Since you appear to have a Mac with USB 3.0 ports, you want to buy a USB 3.0 hub for maximum speed for the devices that can use it.

As you have an iMac, you might be interested in this, which I saw the other day:

https://deals.macnn.com/sales/aluminum-usb-clamp-hub

Using Thunderbolt for USB through adapters like chas_m suggested also get an older Mac USB3 while the cheaper powered hub only provides more USB2 ports. Either way works, but USB3 is really nice and speedy!

EDIT: I didn't see that the OP has USB3-capable Mac, but this tip is good for those of us that don't have USB3 machines. (Maybe next time I'll pay more attending!)

Chas-m...the clamp on hub looks really neat. I'll look for one in the uK.
I've got the latest iMac so have USB3.0.
Also found this...
Thunderbolt™ 2 Express Dock HD with Cable
It's a bit pricy so perhaps in the future?