The WRT55AG is a dual-band (A + B/G) wireless router + 4 port switch. Its featureset as shipped is much like the LinksysWrt54g, with the addition of 802.11a support.
There are two versions of the WRT55AG V1 and V2. You can get the version number from the sticker on the bottom of the device.
I'll start with some internal V1 pictures:
Source code to the firmware: http://www.linksys.com/support/opensourcecode/wrt55ag/wrt55ag.1.1.tar.gz
Firmware updates: http://www.linksys.com/download/firmware.asp?fwid=181
Product page: http://www.linksys.com/products/product.asp?prid=537&scid=35
See also:
http://wiki.openwrt.org/OpenWrtDocs/Hardware/Linksys/WRT55AG
