Perhaps Debian. Try a live Debian Linux like Knoppix. Easy to install and maintain ('Poorman' flavor) . remember, always run a firewall. I can offer some economic linux consulting services. If you are interested in some quick tips and easy solutions, please PM me. Or you can always find best free solution yourself in the wonderful Linux community.
That is a loaded question. For the desktop, Redhat. For the 32 bit server, FreeBSD. For the 64-bit server, SuSe. nitro