How can I get deals on flight to Denver and San Fran emailed to me

Is there some website that has closeouts, or last minute deals, or
some other killer deals on flights to/from LA and Denver and/or San
Francisco?

I am willing to fly anytime.  I can book months in advance, or at the
last minute.  Whatever will get me a better deal.

Coach class, of course.

Is there a bot of something that looks for special deal between any 2
cities and will email you when it finds something below a certain
amount?

thanx in advnce

JohnnyJet is fabuluous:
http://www.johnnyjet.com/home.asp

Southwest (southwest.com) offers daily web fares through its Ding!
program -- install it on your computer and at least once a day you
will receive notifications about special rates to and from different
airports.

Haven't tried it, but it claims to do just what you're looking for:
http://www.bigfuntravel.net/farewatcher.htm

Of course, tons of websites provide weekly letters with good deals and
some allow for a bit of customization but not exactly what you're
looking for, including:
cheapflights.com, bestfares.com, smartertravel.com, travelzoo.com, priceline.com.