What recording device should I use for recording games online that won't lag my game?

I wan't to make a Let's Play series but every time I record using Camstudio it lags my game any idea how to fix this?

The three things that will speed it up are decreasing frame size, decreasing frame rate and reducing the color settings.

I suggest that you use fraps. You can download the free trial from fraps.com
But this only gives you 30 seconds of recording time

If you want it longer then you download the cracked version of fraps
Go to google and look up 'fraps crack' and choose any of the following that you believe is safe. Have fun