Mostly for fun, I got a Foscam FI8910W for Christmas. They run about $90 each, so it's a pretty cheap solution. It works well, but you have to be reasonably techie to set it up since you'll have to mess with the ports it uses and port forwarding on your router to get it working.
The only thing I'll say to look out for is that many of the IP cameras function fine, but their software is very limited. Given that mine is just for fun, I hooked it up with a little site called Mangocam and use that to just record pics for a bit when motion is detected. There are subscription-based sites out there that can handle long-term recordings and that kind of thing.
If you're wanting to run multiple cameras and have them recording all the time, you might want to consider software to run on a local desktop computer rather than uploading to the cloud. These things take up quite a bit of bandwidth, so they can drag your internet connection down pretty badly if you're not careful.
If you happen to look seriously, I can give you access to mine for a bit so you can check it out and see how it works. Here's a pic of my cats
just so you can see the quality.