Documentation can be found on www.aircrack-ng.org See also manpages.
Madwifi-ng known bugs:
When changing rate while you are capturing packet makes airodump stall
Solution: restart airodump-ng or change rate before starting it
You can use airodump-ng on OpenWrt devices. You'll have to use specify prism0 as interface. Airodump-ng will automatically create it. Rq: Aireplay doesn't work on such devices since the driver doesn't support injection
(except those with an Atheros card)