Factory lead time is listed as 16weeks. It looks to me like they are rotating production on limited lines.
This seems to be due to the economic collapse, remember theres no inventory anymore, its all premised on ‘just in time’ delivery…cool huh?
(caveat: this may be for the US only, since a) the usa does not manufacture much electronics, and b) IF, big IF, the reports of Chinas exports are true, they are using up all the supplies…again IF true. All of Asia is likely higher priority than USA).
328s are out too, but it ‘appears’ that the real production-to-delivery is about 4 weeks, as mouser lists 5 small shipments about 4weeks apart.
EDIT: I was right, search for a vendor out of HongKong, they have tons of them. http://www.ic2ic.com/search.jsp?sSearchWord=ATMEGA168-20PU