I finally got around to setting up a server at my store i am installing a wsus server and looking to installing a cache is there a good free one out there?.
It's called a caching proxy. Squid is an example of one. ISP's often use the 'transparent' mode. All this takes a bit of doing and can cause refresh confusion for the end-user and there can be site compatibility issues.
I'd stick to setting up WSUS and have your workers cooperate in maintaining a shared software folder.
You could set up IPCop with the Update Accelerator addon.
You can configure the normal web proxy cache, then have additional options to cache updates (for all OS types or download sources (like nvidia drivers, for example) with the addon.
I was using IPCop on an old PIII until about a week ago when it's hdd decided to throw up an error.
IPCop hasn't been updated for a year or two so I've rebuilt it with Smoothwall which is updated and fantastic. You can set it's proxy to be transparent so you don't need to change any settings on the client PC.