Three SD cards tested, see here what is write on them:
What they write on label - click here
Tested with h2testw_1.4 (google for it, it's free and small).
Results:
Sandisk Extreme class 6 (20 MB/s* on label) - 4 GB capacity
Writing speed tested: 12.3 MByte/s
Reading speed tested: 14.1 MByte/s
Sandisk class 2 - 8GB capacity
Writing speed tested: 5.40 MByte/s
Reading speed tested: 7.32 MByte/s
HAMA class 6 - 8GB capacity (don't know why Hama has a 10 in a circle and a 6 in another circle).
Writing speed tested: 12.3 MByte/s
Reading speed tested: 14.0 MByte/s
Trust me, on a DSLR camera in high speed mode you will shoot about 6-7 photos at high speed and after that the buffer will be full and SD card write speed limit will slow you down. Let's say you shoot RAW+Jpeg fine, this is about 11 MB+5MB (body with 12 MP sensor). So, after first 6-7 photos you will have to transfer on card about 16 MB. On a card with ~ 12 MB/s this will be more than 1 second. On a class 2 card (5.4 MB/s in my test) you will wait about 3-4 seconds before next shoot!
Conclusion: buy faster and more expensive cards if you are a sport or action shooter.
See ya! Dorian King out. (click on Useful you lazy!)