Because of the distance, you will need a high-gain antenna such as a yagi (a cantenna is a type of yagi) -- or a parabolic -- at one end, at least.
Depending upon the distance (and what kind of obstructions are in between), you may need high-gain antennas at each end. Of course, you'll have to carefully point the antennas at each other. (You may need to have someone at each end -- in contact with each other via walkie-talkies or cell phones -- to make small adjustments until you get maximum signal when you set everything up.)
Clear "line of sight" is best. Completely clear of trees or whatever if possible. Any obstructions (windows, walls, or even just trees) will significantly reduce the strength of the signal. You'll definitely need high-gain antennas at both ends if you have any obstructions ... and even then, the signal strength may end up being too weak.
If you can manage to hook up a good antenna to your computer in your new house and point it directly to your mom's house, that should work. Otherwise you may need a 2nd wireless access point at your new house, which has a "wireless bridge" capability compatible with the AP at your mom's house. Put their antennas on the roof of each house (pointing directly at each other), with as short a cable as possible between each AP and its antenna. Depending upon the make/model of the 2nd AP, you may be able to also be able to use the 2nd AP as a local AP in your new house in addition to its "wireless bridge" function.
[I've a couple of setups similar to this, including one at a large outdoor soccer complex where LOS distances ran up to 2km. We used yagi's out on the fields, all pointing to a central (fairly tall) omni antenna in a "point-to-multipoint" setup. Clear line of site was essential at that range with those kinds of antennas in order to get really good signals.]
If you end up placing antennas outside (on roofs or whatever) be sure to bolt your antennas onto something sturdy. If you're using poles, use as shortest, strongest poles you can. Otherwise you'll lose your antenna aiming whenever the wind picks up.
Hello, I might be moving out of my mom's house and into a house 2 blocks away. I would like to "borrow" the wifi from my mom's house from the other house. Does anyone have any suggestions on the cheapest way to go about doing this? I was thinking a cantenna pointed right at my house from the roof of the other house and some kind of cheap linux box set up as a repeater in the attic or something. I love kismac btw :).