Reverse/Server-Side Proxy Caching for Windows?

frooyo asks: "I'm an currently looking for a good reverse proxy caching solution (server-side caching) for the Windows platform. This would be used as a transparent proxy between the corporate website and the outside world. Products that I have seen available include: Microsoft ISA server, Squid for NT and some others. I'm not completely opposed to using a non-windows platform for this type of solution, but I would prefer a Windows solution. I need a product that handles middle-large numbers of current users (10-30) with easy on one server. Additionally features such as caching pools and easy handling of FTP connections (since this will be used as a 'transparent' proxy) would be a much needed benefit."