I mainly use IP webcams made by Axis (http://www.axis.com). The model of camera I use is the 207W (http://www.axis.com/products/cam_207w/index.htm), which has its own web server for viewing the live image and for configuration etc. It supports motion detection, audio and video recording and can upload images and videos to an ftp server or via attachments to email. It can be hard-wired or operate over a 54g wireless network. It’s basically a mini Linux box with a camera attached. The picture quality is good compared to other cameras, maximum image resolution is 640x480 @ 30 frames/second. It’s not cheap, Amazon currently sell it for £260. They do a cheaper model without wireless (the 207) for £242 and a bottom end camera (the 206) for £208. It is not weatherproof though, for full outdoor cameras you need to spend a lot more – something I haven’t ventured into. Reliability-wise, mine (I have two Axis 207w’s) have been fine for 2 years. They will run for months without needing any attention.

Because the axis cameras are self-contained units, they don’t need a pc to operate. They just basically need an Internet connection. They support dynamic DNS so you can configure them to update their ip address against a DNS name automatically if you need external access to the camera. I basically use mine without direct external access and just get them to upload images via ftp when the motion detection is triggered. All I have is a web site that displays the images in sequence (the camera can be configured to index the images up to a given number and then overwrite the oldest). There’s a good review of them here http://www.trustedreviews.com/networkin ... -Camera/p1

I do have some software I run on a pc if I want to use USB cameras or less versatile ip cameras. It’s called VisionGS and is the best software I’ve seen for this purpose for the price ($30). You can get a demo copy here http://www.visiongs.de/ The Axis cameras will work with this software too, but really you don’t need to because they can perform all of the software functions autonomously.

I’ve also got an older Linksys ip camera but I don’t rate it compared to the Axis products.

Perhaps a security light would be enough to scare them away?

I was looking into security cameras for a company a few years back.

Plant roses or gorse bushes. Nothing like some dangerous spiky plants to help with security.

That's actually a pretty good plan. Make the route as unpleasant as possible.
Unlike razor wire and other solutions offered, there is nothing to stop you planting really nasty sharp plants.
I used to water the gardens of a hotel, and they had the front hedge full of very unpleasant spiky things. The biggest hassle we had was people leaving crisp packets in it on their way home from school.