This month and next I'm giving you an overview of using Linux to manage file and print serving for your Windows machines, share your Internet connection, and security. Functionally, they do the same things. In my opinion, however, Linux does it better. This is a grand use for your old 486 or elderly Pentium.
Some hubs come with an uplink port.
This lets you link to another hub for easy expansion. Any PC 4 years old or newer has PCI slots. PCI NICs give the best performance, if you have a choice. ISA cards are OK, if that is what fits your computer, or if saving a couple of bucks is important. For laptops, cardbus or 32-bit network cards perform best.