Current showtimes are available from
Yahoo and
IMDb.
Only major theaters are available here, so
you may want to try another more
general
entertainment site for obscure venues (e.g. in DC, the
French Embassy, the National Gallery, and the Hirshhorn each have
pseudo-weekly high-quality film series) and repertory houses.
To find a movie to rent, try one of Yahoo's
list of personal preference predictors (I found the MovieCritic site most
helpful), which ask you to rate several movies and then match you
with other individuals in their database who have similar preferences
to find other movies you might like. The more movies you rate, the
more accurate the predictions.
Amazon
and IMDb
have lists of award-winners (Oscar,
Cannes, Venice, etc.), the
AFI top-100 lists, and
user ratings.
To find info on a particular film, check out:
An exhaustive movie database (with complete cast and crew):
IMDb.com
The industry standard: