It depends what do you want to do exactly, something easy to set up, or several cameras, monitors and professional setup. Well, here I have an article about the topic: Webcam surveillance

In fact I just want to be able to check what happen at home while in at work

Thanks for the article, I will take a look at the softwares you propose and see if it fits my demand.

I would recommend something that works for me: a few motorized IP-cams, connected to your Internet router. There are 3 major advantages: Contrary to a classic webcam, an IP-cam doesn't need to be connected to a live computer to operate. Second, they don't need any additional software, since every cam has an integrated web page that gives you access to its image and setup (and more, see below). And third, a motorized cam gives you much better coverage than a fixed one, requiring less devices. Only downside, they're a bit pricier, but still no comparison to a professional video surveillance system...

I've tried literally a dozen models, and I found the Panasonic range the best by far (not the cheaper, though... go figure!). For ethernet only, I recommend the BL-C11IP model. If you want the added flexibility of Wi-Fi, then go for the BL-C131CE. And if you want to put them outdoors, then it will cost you a bit more yet for the outdoor-capable BB-HCM371A.

A nice touch, each camera's internal webpage gives you the ability to display the images of 3 other cameras as well as its own, thus enabling you to look at all 4 cameras at a glance while accessing just one. They also have the ability to broadcast fixed 640x480 snapshots at predetermined intervals to an ftp or website, stream the image to a smartphone, etc.. This makes any additional software completely superfluous, as a simple browser will suffice except if you want to do continuous recording.

To access the cameras from outside, you just need to have a free dynamic DNS account set up, like with dyndns.org if your router/box supports it, or else you need to have a fixed IP address. Each camera can be given a local IP and a different port (instead of the classic port 80), and the router configured to transfer incoming streams for each port to the appropriate address.
As an example, if you have 2 cams, you will give the first one IP 192.168.0.100 and port 1000, and the second one IP 192.168.0.101 and port 1001. Then, you will configure your router's firewall to transfer all incoming traffic directed to port 1000 to IP 192.168.0.100, and the one for port 1001 to 192.168.0.101.
If you want to access your cameras internally you just type the full local address (192.168.0.100:1000), and if you come from outside, you type http://(your_dyndns_id).dyndns.org:1000, and there you go!

Hope this helps.

@ Roger: It's sounds like the most appropriate solution (I think I will remove the "motorized" option because of the price and I don't think I'll need it if I put them on strategic places)

Thanks also for the "how to" at the end, you almost get all the job done, just have to buy the IP cameras :)

@ Nice answer sir, I might check it out myself.