Programmable system on chip (SOC) pluggable on a host via PCIe
I'm not really sure if this is what you're looking for, but thought it might be useful.

http://www.advantech.com.tw/products/PCE-5120/mod_B16C5C03-4498-49DD-BEF8-1ECF1890B322.aspx

From the site:


  LGA775 Core™ 2 Duo Processor Card with
  PCI Express/VGA/Dual GbE LAN 
  
  Complies
  with PICMG 1.3 Supports LGA 775 Intel®
  Core™ 2 Duo with 1066/800/533 MHz FSB
  Supports dual-channel DDR2 533/667
  SDRAM up to 4 GB One PCIe x16 and four
  PCIe x1 links to backplane Dual
  Gigabit Ethernet via two PCIe x1 ports
  Onboard IPMI module (optional) Four
  SATA2 channels with software RAID 0,
  1, 5 and 10