The links you posted only differ in that one includes an SD card, and one does not.  The 512MB Model B hardware is the one you want.

If you're just getting started with the Raspberry Pi, I recommend checking out 'Starter Kit' bundles.  Usually a starter kit will include, at minimum: Raspberry Pi, power adapter, SD card and case.  Some starter kits may include more.

You will also need an ethernet cable, USB keyboard and mouse, monitor, and cable for monitor (HDMA or RCA video)

Some places you can pick up a starter kit:
(these links do not represent endorsement, just examples to get you pointed in the right direction)

http://www.amazon.com/CanaKit-Raspberry-Complete-Original-Preloaded/dp/B008XVAVAW/
http://www.mcmelectronics.com/product/RASPBERRY-PI-RASPBRRY-PCBA-/83-14275
http://www.newark.com/raspberry-pi/raspberry-pi-starter-kit/model-b-starter-kit/dp/72W4007
http://www.maplin.co.uk/p/raspberry-pi-board-and-starter-kit-r45pi
http://www.makershed.com/Raspberry_Pi_Starter_Kit_p/msrpik.htm
http://www.adafruit.com/products/1014


Hope this helps!

EDIT: Starter kit bundles usually include a Raspberry Pi, too