SD Cards and Preformance on the Pi

SanDisk 16GB Extreme SD SDHC Secure Digital Card UHS-I Class 10 45MB/s 300X (SDSDX-016G-X46) - Retail Package

Costs $20

On latest Raspbian ( Linux raspberrypi 3.1.9-cutdown+ #270 PREEMPT Tue Aug 7 22:42:04 BST 2012 armv6l GNU/Linux )

Speed results as per testing guide:

Write 18.4 MB/s

Read 21.4 MB/s