I don't often recommend specific pieces of hardware, especially in the context of OpenSource, but this one deserves it.
Rosewill RNX-GX4 IEEE 802.3/3u, IEEE 802.11b/g Wireless-G Broadband Router
Having avoided wireless Internet for as long as I possibly could, I went into a recent search for a good wireless router with no small degree of trepidation and a lot of ignorance. I literally spent two months researching various options before deciding on my final purchase. My initial instinct was to go with the Linksys WRT54GL both because it is popular and because a previous revision of it was powered by a Linux kernel. Moreover, the router could relatively easily be modified with third party, OpenSource firmware. What I discovered, though, was that Cisco/Linksys had abandoned that philosophy. Their current revisions of this router model work with proprietary firmware and are quite a bit more difficult to modify. Turning them into bricks is common among those attempting to do so.
So, the search continued, and I eventually found this:
http://www.newegg.com/Product/Product.aspx?Item=N82E16833166032Rosewill is a name without much prestige. It's commonly known as the bargain basement brand for computer hardware, although I have personally purchased several of their products in the past (specifically cases and a few power supplies) that were quite good for the price, the power supply having been functioning perfectly all this time in a system I built over five years ago. When I read about the router, I decided to give it a shot and have been wonderfully pleased by it.
The router comes with its own firmware, but the device is specifically built for and marketed towards those who want OpenSource options. The router easily accepts two of the most common versions of OpenSource firmware, and to make things even better, the manual you receive with the router gives you instructions on how to install it. Not even the Linksys model, when it was popular among OpenSource consumers, did that.
I've been using the router for two months now. The firmware that comes pre-installed is perfectly adequate for most people, but I've tried different variations of third party firmware, and those worked well also. The one I liked the most unfortunately didn't not support WPA2 encryption, so I abandoned it, but future updates of it are promised to include it. Range is good. It comes with two adjustable antennae, and in my place I am getting a signal through two walls, one of which has plumbing in it, and maintain 100% signal strength most of the time with typically Bit Rate=54 Mb/s and Tx-Power=20 dBm.
BTW, it's also cheap. Suggested retail is 44.99. I got it from NewEgg on sale for 29.99.
If you're in the market, I highly recommend it.