The Linksys WRT54G is ubiquitous, and I recently added an ASUS RT-N66U (not the latest and greatest, so a little cheaper) works very well and has some extra bells and whistles (can act as a file server).
While it is true that the WRT54GL was _the_ goto firewall router for the 2000s, it is too slow to handle today’s high speed broadband connections (Comcast now routinely bursts at 50mbit/s even on a Starter 12 mbit/s plan.) Also doesn’t offer 802.11n or 802.11ac WiFi, which is needed for 1080p.
I upgraded to the TP-LINK WDR4300 because it has all the needed specs for a good price: 128MB mem, a fast ARM SoC, USB for JFFS storage, dual-band antennas, and best of all flashable to OpenWRT.