802.11a
Sometimes, it's just time to move on. If your efforts at battling 802.11b / g interference are proving to be futile, consider changing to 802.11a. Contrary to what you've probably read, current-generation 802.11a products have performance equal to or better than many 802.11b and g products. And since they operate in the relatively quiet (at least for now) 5GHz band, all the neighboring 11b and g WLANs that are causing you so much grief will, for all intents and purposes, disappear.
If you go this route, avoid single-band, i.e. 11a-only products. They all have first-generation technology, which did have inferior range. (See the Second-generation 802.11a NeedToKnow for more info.)
Shop only for dual-band (11a / 11g) or dual-band, tri-mode (11a/b/g) products. Also be sure to hit the shopping search engines and check for bargains since products containing 11a seem to move slowly and retailers occasionally like to clear out inventory.
Updated March 6, 2004
NOTE: A helpful reader pointed out that there are still some dual-band products out there that have first-generation 11a radios - most notably, the Linksys WRT55AG .