Summary: 2.6.26 adds support for

• read-only bind mounts
• x86 PAT (Page Attribute Tables)
• PCI Express ASPM (Active State Power Management)
• ports of KVM to IA64, S390 and PPC
• other KVM improvements including basic paravirtualization support
• preliminary support of the future 802.11s wireless mesh standard
• much improved webcam support thanks to a driver for UVC devices
• a built-in memory tester
• a kernel debugger
• BDI statistics and parameters exposure in /sys/class/bdi
• a new /proc/PID/mountinfo file for more accurate information about mounts
• per-process securebits
• device white-list for containers users
• support for the OLPC
• some new drivers and many small improvements

more here