You could use the Raspberry Pis themselves along with multixterm on your main computer to "boot strap" your SD card writing. You should be able to find multixterm in many distro's package managers.
Step 1: Buy a bunch of the USB stick SD card adapters.
Step 2: Use the standard methods to write 2 of the SD card images with your main computer.
Step 3: Put the 2 SD cards with images into 2 Raspberry Pis and get them connected to your network and powered up.
Step 4: Put 2 empty SD cards into the USB stick adapters and plug them into the 2 running Rapsberry Pis.
Step 5: Now here's where it gets interesting, from your main computer use multixterm like so from the command line multixterm -xc "ssh %n" host1 host2 where host1 and host2 are the ip addresses of the Raspberry Pis.
Step 6: Inside of multixterm's stdin window you can use dd as you normally would to write images to the SD cards but now multixterm will send that dd command to both Raspberry Pis simultaneously.
Step 7: Repeat steps 3-6 until you have all of your cards written.
The more SD cards you image the more Raspberry Pis you can use to image new SD cards. Obviously this technique won't write all of your cards in one go, but it would cut back on the amount of time it takes to complete writing all of the cards. This technique would be largely experimental so your mileage would vary, but the theory of it sounds like an interesting experiment...