alpha release

http://www.postgresql.org/developer/alpha

has a link to

http://developer.postgresql.org/pgdocs/postgres/release-9-1-alpha.html

...which no longer exists, as Bruce has generated the regular release
notes that will eventually be used (after further hacking, doubtless)
for the final 9.1 release:

http://developer.postgresql.org/pgdocs/postgres/release-9-1.html

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company