OpenWRT is lightweight Linux distribution targeting routers. It runs on very limited resources, usually ARM or MIPS architecture with only 16-64MB of RAM and 2-8 MB of Flash.
iMX233-OLinuXino is noW officially in OpenWRT trunk which makes very easy to build OpenWRT image for OLinuXino
In OpenWRT WIKI is given detailed description how to prepare SD-card when you have the images: http://wiki.openwrt.org/toh/olimex/imx233-olinuxino
To build OpenWRT from the sources you should do this:
# git clone https://github.com/mirrors/openwrt # cd openwrt # make menuconfig then Select Freescale imx233 + Olimex boards Save and quit # make -j10 precompiled files are available at: http://filez.zoobab.com/openwrt/imx233/openwrt/bin/imx23/