Hi,
I am planning a project with one or more TLC5940s and an Arduino with Ethernet.
There is a note on the hardware page of the "Arduino Ethernet", which says
NB: Pins 10, 11, 12 and 13 are reserved for interfacing with the Ethernet module and should not be used otherwise.
Is that true? Is it not possible to connect another SPI device?
Would the Ethernet Shield or some other hardware allow me to do that?
Best regards,
Flyser 
Is that true? Is it not possible to connect another SPI device?
Yes and no. Yes, the pins are reserved for SPI use, of which Ethernet is just one device. No, the pins are not reserved EXCLUSIVELY for the Ethernet shield. Other SPI devices can be connected, including the on-board SD card.
Would the Ethernet Shield or some other hardware allow me to do that?
As long as you use a different slave select pin, yes. Pins 4 and 10 are already used, for SD card and Ethernet, respectively.
Based on my (rather limited) knowledge of the SPI bus, I assumed the same, but then I found this:
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1248045864/5#5
Is this information outdated or just wrong?
Thanks for the quick reply,
Flyser