Looks there is a lot of work going on at TI, Linaro and Canonical to support OMAP3 and OMAP4 chips in upcoming 11.04 Natty including 3d acceleration. They currently support beagleboard and pandaboard.
few random links
http://cdimage.ubuntu.com/ubuntu-netbook/releases/natty/alpha-3/
https://wiki.ubuntu.com/ARM/OMAP
http://old.nabble.com/Natty-ti-omap-rebased-to-2.6.38-final-td31178078.html
https://launchpad.net/~tiomap-dev/+archive/release