In this case, SOHO stands for "Small Office / Home Office," a type of local area network (LAN) designed to be used by a very small business. Like other LANs, a SOHO network can be a mixed network of wired and/or wireless computers. Being a business network they also tend to include printers and sometimes voice and fax over IP technology. A SOHO router is nothing more than a traditional broadband router marketed for use by such organizations. These are often the same routers made by Linksys, Netgear and others used on ordinary home networks.
Just how small is the 'S' in SOHO? Wikipedia claims these networks typically support between 1 and 10 people. But there is no magic that happens when the eleventh person or device joins the network. In practice, SOHO routers can support somewhat larger networks than this. What are some practical limits on the size of a SOHO network that you've seen?
→ See also - Small Office / Home Office (wikipedia.org)

I must confess that my knowledge in networking has greatly improved, ever since I know this site ‘about.com’.
Thanks to about.com crew and Bradley Mitchell for the newsletters updates.
A beg to disagree with you, SOHO routers are a bit different from your run of the mill router available at your favorite big box store. In my small office of 5-15 people (depending on the day) we use to have I think it was a home netgear router, it was junk, the range could not cover the office, you had to reboot it once a week and people were constantly getting kicked off. In comes a Cisco SOHO router, completely different story, the range covered the office, you never had to reboot it, no dropped connections. That sucker went for over 3 years only retired when the company was bought out and the new parent company put us on their network and replaced it with real enterprise wireless router.
If you have actually ever configured a CISCO SOHO router, it’s not easy, allot of very technical screens to do simple things, nothing at all like a home router configuration.
I am thinking about bighting the bullet and getting a SOHO router for my home, it is worth paying 5x-10x more, it really not the same thing.
Interesting Bill,
I had the exact opposite experience. Started with a cisco soho router for our site. Had way too many disconnects/outages. Replaced with Netgear, problems gone!
JM