.:: Wireless Web Camera ::.
There are a few wireless webcams I can recommend from personal experience, you should be able to buy them at Amazon or maybe pick them up cheaply on Ebay:
1) Panasonic BL-C131A
The Panasonic BL-C131A has a built-in web server. You can connect it to your home network by ethernet cable or use its wireless interface (though you will need an ethernet connection to set it up initially). Once it's configured properly for wireless mode, you can just place the camera wherever you want (you'll still need to connect it to a power outlet, of course).
Officially, you will need a Windows PC with IE and ActiveX controls to access it, which seems to be a common disease with web cameras. But this camera works fine with a Macbook and either Safari or Firefox, even if none of that is supported by Panasonic. It even has a heat sensor which you can use to trigger recording or an email alarm when someone enters the room.
It's not the cheapest model, but great value for its price.
2) Linksys WVC54GCA Wireless-G
This is a pretty cheap one (usually < $130) with a built-in webserver, it's also very compact and reliable. It has a pretty cool security feature that allows you to make it send an email to up to three different addresses once the camera detects movement in a predefined area. Only problem with this webcam is that it needs ActiveX during the initial setup, so you'll need a windows box with IE to configure it.
3) Allnet ALL2281 IP-Cam W-Lan
Even if it looks a bit strange (like a babyphone or something), this is actually a pretty decent camera with very good features. It even has a built-in infrared lens that provides clear images in darkness or low visibility conditions, so the camera can deliver video streams during the day and night. It also captures audio, and it has an USB-port so it can record directly to USB memory sticks or harddrives.
4) LogiLink WC0002B WLAN Cam
That's also a really cheap one, I bought it for something like $69. The camera has its own web server which can be used to configure it. Images can be sent by mail or uploaded by FTP, the motion detection feature offers different settings like sensitivity, notification by email, picture to mail and/or FTP, and so on. The software can be used to build a simple home security camera system if you have more than one of these cams. Image quality is what you can expect for this price - let's say it's sufficient. All in all a great low price solution.