I'm using used Cisco, Nortel and Dell gear purchased off eBay at home extensively. YMMV.
I've picked up Cisco 7200 and 3600 routers for less than $250 with a couple of 100baseT interfaces that can route and basic firewall at wire speed. Even a 4700 with 2 100baseT interfaces can keep up (barely). Just make sure that you get the software image you need, as you have to pay to upgrade (or steal it).
I'm pretty 'meh' on Cisco switches. They command a premium, and really aren't superior. I'd never pick up a Cisco chassis switch for the house; too loud and too much power draw. The Cisco gigabit switches generally are wildly overpriced. Almost anybodies gig copper managed switch can handle the home load. That said, if you have access to fiber NICs (dirt cheap), GBICs and fiber cables, things like a C3550-12G, C4812G and C3508G are going for dirt and are solid switches.
Dell switches are a tremendous value, especially considering the feature set (VLANs, QoS, LAG/LACP, etc). They upgrade the lines quickly (creating turnover on the secondary market), update even old ones and the software updates are free.
Nortel BayStack switches go for basically pin money because Nortel is no more and enterprise users are dumping them as fast as they can. They're every bit as good as the equivalent Cisco. Avoid the Nortel firewall/VPN gear; you really need to be able to get software updates on those, and you won't.
There's a vast amount of enterprise WLAN gear being dumped for pennies because most everyone is upgrading to 802.11n. I see keeping my 11a gear for years, as 54/108Mb is enough for almost everything an end-point needs short of 1080p streaming and 5GHz keeps you out of baby monitor and cordless phone hell. Just don't pick up anything that needs a controller to be useful.
P.S. - What everyone else said...get a UPS. Seriously.
P.P.S - Look at things like Vyatta and Linux/BSD based alternatives. Other than switches, I've pretty much ditched my enterprise options for these. I'm running them on retired, last generation, enterprise Dell servers. Loud, but rock solid.