These are the cameras I am using to helping a friend upgrade his existing system:
http://www.amazon.com/USG-5MP-Bullet-Security-Camera/dp/B00LEIEC6K/ref=sr_1_2?s=electronics&ie=UTF8&qid=1419657538&sr=1-2&keywords=USG 5MP camera
He has an existing system with a 16 port capture card but the 12 cameras are older camera that use an NTSC signal so they are standard definition rather than HD. Standard defintion is about 640x480. The cameras listed above can do 1080p 1920 x 1080 @ 30 fps or even 2592 x 1920 @ 10 fps.
We will connect a few of the new cameras to a Power over Ethernet (PoE+) switch so he only has to run one cat5 from the switch to each camera.
http://www.secureitstore.com/SG300-10MP.asp?gclid=CI2S3e3T5cICFeLm7Aod6WMALg
We are going to change the software on his existing Windows 7 DVR system over the Blue Iris.
http://blueirissoftware.com/
Blue Iris will be able to record from both the existing capture card and the new IP based cameras. I have not used Blue Iris yet other than installing the free demo but have heard good things about it.
I have confirmed Blue Iris is compatible with the cameras listed above.
You can use some IP webcams without a computer and record to an SD card in the camera. Some cameras have a web server built in to monitor the live feed or to review saved motion. If you only need one or two cameras that might be an OK option for you.
edit: Originally had this PoE switch
http://www.newegg.com/Product/Produ...62205&cm_re=PoE_switch-_-33-150-153-_-Product
but changed it to a PoE+ switch since the camera specs say 2A@12V which is 24 watts.
PoE is the 802.3af standard with a max of 15.4 watts
PoE+ is the 802.3at standard with a max of 25.5 watts