Guide to small business networking

The cloud is free, for the moment. Look for online collaboration tools like what Google has; or search for SaaS - Software as a Service model. SaaS works quite well.

Really, the hardware is plug and play. Just buy a good gigabit switch from somebody like 3COM, and hook your PC's to it via Category 5 factory-terminated cables, and you've a small business network.
Software-wise, just use MS 2008 Server R2 SP1 for the Directory, File, Print, and Database Services on a dedicated piece of hardware, like a powerful PC, and you're done.