Stupid 802.11b Tricks
The only thing limiting the range of 802.11b (in the U.S.) is Part 15.247 of FCC Rules and Regulations. This regulates the 900mhz, 2.4 GHz (802.11b), and 5.7 Ghz (802.11a) unlicensed bands. Concerning 2.4 GHz, Part 15.247 limits the power output of the Intentional Radiator (your 802.11b wireless card) to one watt of power.
There is, of course, work arounds.
The FCC will let you have about four times the base power (6dBi) as long as you are using a directional antenna. This is nice, especially for mobile applications that aren't within five hundred meters of your base station. This is allowed because with a directional antenna, you aren't just dumping your power in all directions, but aiming it at a certain location. Cleaner, and less noisy.
If you wanted to set up two fixed wireless locations communicating with each other, you can hack it up a little more, and get around ten miles at full 11mb/s bandwidth. The catch is, the two directional antennas need to stay pointing at each other, setting up a permanent wireless LAN. Otherwise, you would have to stick with the above, "directional antenna", restrictions.
Once you go past a certain wattage of output from your directional antenna (30dBm base, 6dBi gain, 36dBm altogether), you have to start pulling back on power output from your intentional radiator. Strangely enough, this isn't a problem for most 802.11b users, because their cards don't put out more than 15dBm, or .03 Watts of power (3% of the maximum).
There is good smarts behind the restrictions, though. If you were to use a discarded Primestar Dish (which I use) at the full one watt output of your intentional radiator, you would, with the parabolic dish's gain (around 27-31 dBi well configured), achieve 1000 watts in a concentrated area. My microwave puts out 1200 watts.
Knowledge (or information) truly is dangerous.