http://www.opencores.org/ Open Cores Repository.
The Open Cores web site seems to be the central repository for a wide variety of computer peripheral designs and is definitely worth checking out. The Open Cores site has a link page to other resources, so I won't include them all here.
http://www.fpgacpu.org Jan Gray's Risc CPU Web Site
Jan Gray has a XR16 RISC CPU , GR000 RISC CPU and XSOC (System on a Chip). He also runs the FPGA CPU mailing list.
http://www.itee.uq.edu.au/~jwilliams/mblaze-uclinux/ John Williams MicroBlaze uCLinux Web Site.
John Williams is a Professor at the School of Information Technology and Electrical Engineering at the University of Queensland. He runs quite an active mailing list for implementing uCLinux on the Xilinx MicroBlaze soft-core processor.
http://www.birdcomputer.ca/ Robert Finch's Bird Computer - FPGA Cores
Robert has a variety of CPU, video, audio, timekeeping and keyboard projects for download on his web site.
http://www.fpga4fun.com/
Various FPGA projects for the hobbyist. Includes information for connecting devices such as LCD Displays and R/C Servos to FPGAs.
http://www.retromicro.com Doug Hodson's Web Page
Doug has implemented a few projects using the XESS XSA100 FPGA Board. Doug's project page has some examples of VGA video generators. The XSA is quite a nice little board with Flash memory and Dynamic RAM, although the XSA100 uses a smaller FPGA and access to static RAM conflicts with some of the I/O pins. The XSA100 uses a XC2S100 FPGA and can be purchased with the XStend prototyping motherboard. For more details check out  http://www.xess.com . They have all the manuals on their web site. The XESS documentation is quite good.
http://www.fpgaarcade.com
MikeJ's complete PACMAN, Space Invaders, and Galaxians in FPGA !
http://members.iinet.net.au/~msmcdoug/ Mark's Perpetually WIP Home page
Mark's Vic20, ZX81 and Arcade game web page. (Also includes some work on the CoCo).
http://www.geocities.com/gary_l_becker/ Gary's OSI-APPLE-SOC
OSI-SOC is a project to build an enhanced Ohio Scientific Inc Superboard / C1P System On a Chip using a Xilinx FPGA (XC3S1000 Spartan 3 Starter Board). OSI-APPLE-SOC adds an Apple ][e on the same FPGA.
http://www.geocities.com/gary_L_becker/coco3fpga.html CoCo3 FPGA
Gary's CoCo3 on an FPGA.
http://www.madscientistroom.org/fpga/
Randy Thelen has a good User Constraint File generator amongst his FPGA bits and pieces.
http://www.cs.ucr.edu/~dalton/i8051/
The Dalton Project at the University of California Computer Science Dept in Riversdale have an  Intel 8051 core. There is a synopsis model as well as C++ simulator for the 8051.
http://www.dte.eis.uva.es/OpenProjects/OpenDSP/index.htm
The Department of Electronic Technology at the University of Valladolid in Spain have an Open DSP design which can be found on their web site.
[url=http://tech-www.informatik.uni-hamburg.de/vhdl/vhdl.html]http://tech-www.informatik.uni-hamburg.de/vhdl/vhdl.html[/url]
University of Hamburg VHDL Page. Assorted VHDL tools and microprocessor cores.
http://www.opencores.org/people.cgi/info/jesus
Daniel Wallner's  Soft Cores Web site is now on Open Cores with five synthesizable microprocessor cores: PPX16 (PIC16C55, PIC16F84), T80 (Z80), T51 (8051), T65 (6502) and AX8 (90S1200, 90S2313).
http://indi.hpsdr.com/
K Ring Technologies Semiconductor Indi16 16n bit Forth CPU. Designed for Altera Quartus II software.
http://www.gmvhdl.com/downloads.html
Green Mountains Computing Systems have a  MC68HC11 VHDL core as well as VHDL tools and simulators. I tried compiling this core under the Xilinx ISE 4.1 Webpack software and it used 200% of the XC2S200 resource, so it is not an efficient design. Later versions of Xilinx ISE Webpack may be more efficient.
http://www.mcmanis.com/chuck/robotics/fpga/index.html
Chuck McManis has put up a web site with a list of his projects for the B3-SPARTAN2+ board.
http://zxgate.sourceforge.net/
For some fun, projects on the net, using Z80 cpus implemented completely in the FPGA. Daniel Wallner's computers using FPGA T80 cores .
http://server.opensourcedepot.com/
Pat's Open Source Depot. Although there are no FPGA projects listed, Pat used to run a small mailing list for Hobby Computer designers. The mailing list included a small group of people interested in designing with the 6809 and the Burch ED Spartan FPGA boards.