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Linksys WRT54GL. firmware is flashable (in most cases), and highly configurable. But, if all you want is to plug it in and go, any router should work for regular things like web browsing... Just don't count on reliability if you're using a lot of connections (like bittorrent transfers)... Avoid D-Link at all costs.
 
I usually like netgear, though right now I have a Belkin wireless router, which for what I paid for it ($35), I am extremely impressed by it.
 
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