SD Card Interface with DE2 in Verilog

Have you examined the reference designs/tutorials from Terrasic? On the DE2 CD there is a example design: "Karaoke Machine and SD Music Player" which uses a Nios II interface with SD card support.

Depending on how you are planning to do it (ie. using Nios II processor or strictly HDL based), you may want to read up on the Nios II developers guide which documents filesystem support and access using the HAL API provided by Altera.

SD card is probably one of the only features I haven't used on the DE2 before sorry, so can't give you any code :(. But have a good look at the Terrasic design samples and search this forum too for lots of good info.