A couple of words....
802.11G or 802.11B. The advantange, and only advantage G has over B is 54mbps versus 11mbps. They both operate at 2.4Ghz. The encryption available is dependent on the hardware and not the B or G standard. WEP or WPA? WPA is preferable, but both your router and Wireless Card have to support WPA. It makes no sense to get a WPA capable router if your Wireless card only supports WEP.
Routers are getting dirt cheap these days. I just picked up a DLink Wireless Router from Best Buy for $50 bucks that support Wireless G/B. (80.11G Routers are backwards compatible with 802.11B standard), NAT Firewall protection, as well as WPA security. How does it work? Like a champ with my IBM X22 laptop with build in Wireless 802.11b, but my R40 with the built in 802.11A/B is a being a crackwhore.
The difference between 802.11A and 802.11G/B is that A works on 5.4 Ghz. transfer rates at 54 mbps, has a reduced range (due to the higher frequency) and operates on an FCC controlled frequency range.
For the home, I'd say 802.11b is more than enough. Remember the time when Ethernet was 10baseT? 10 mbps? lightning fast?