For example, “branded” sites, like say officedepot.com, tend to have very high conversion rates because a large portion of their inbound traffic is already “buy oriented”, and typed “officedepot.com” directly into the browser to get there.

A smaller business, that gets a larger portion of it’s traffic from non-branded searches, will have a lower conversion rate, because there’s a larger proportion of “non buy oriented” traffic. For example, if some of the inbound traffic came from people typing “officejet printer”, perhaps some of that traffic is looking for downloadable drivers, or a troubleshooting guide. That traffic can’t be converted, because they aren’t there to buy a printer.

All that to say that there’s no specific number that’s a “good conversion rate”. The only thing the number is good for is to measure improvement on a single site. Or perhaps comparing two very, very similar sites.