Some pointers like
this and
that. But that's one side of tuning; the other is making sure that your network applications can send and receive data in large TCP buffer windows (when applicable,) such as tunables in Samba or NFS.
As noted in the latter URL, modern 2.6 kernels do TCP autotuning, which should be fine for most tasks; if you're tuning for a WAN, however, be sure to do it on the gateway, as you don't (usually) need it within a LAN.