Combo modem/router boxes are always garbage. What you want is a good router with a good dedicated modem box. Linksys WRT54GL is a good option (esp. if you want to install a custom firmware like OpenWRT or DDWRT and learn more about Linux
). The latest revisions of WRT54G and WRT54GS (5.0 and later) do not add any new features, but instead reduce the amount of on-board memory and use an ugly VXWorks embedded OS instead of Linux; you cannot run the custom firmwares on them. WRT54GL is essentially a rebranded WRT54GS v4.0, complete with the extra memory. Even if you don't want to delve into custom firmware, the WRT54GL is simply a better piece of hardware. You probably won't find it in brick&mortar stores, but places like newegg.com sell it.
Furthermore, don't buy the draft-N junk; its a waste of money for 99% of home networks, on hardware that might not be compatible with the final 802.11N specs to boot.