You can practically rely on most available off-the-shelf routers.. Depending on your requirements, there's a bunch to choose from. Earlier suggestions of Macsense and SMCs are quite adequate.
To further confuse the matter

, let me suggest another.. Try
Smoothwall linux distro, the GPL version. You need a PC with at least 2 NICs to go with it. Although you could probably survive with a 486 or Pentium Classics, my recommendation is, to use Smoothwall with a used/old Pentium II PC (or any ATX types). They tend to be more reliable than Baby AT powered! I have an old PII-233 HP running smoothwall for my firewall for well almost two years, and still running!
You can also consider M0n0wall or a bunch others.
Regards