Discovering and selecting conferences Last summer, there were several excellent summer schools in my field that I learned of only after the application date. The events I did attend were chosen without too much care. I'm planning for the coming summer, but don't really know how best to go about this. Relying solely on the posters that appear on bulletin boards at the local math department seems inadequate.
How do you learn about the exciting summer schools and conferences in your field? Do you rely on word of mouth? What listings do you turn to? I imagine answers will diverge based on position, so please state at what stage of your career you used this approach.
How do you decide which events to attend? What factors play into your choice? Obviously, speakers and location make a difference. How do you weight such factors?
 A: Kiran Kedlaya's list of conferences in arithmetic geometry. http://scripts.mit.edu/~kedlaya/wiki/index.php?title=Conferences_in_Arithmetic_Geometry
A: Jon McCammond maintains a list of conferences in geometric group theory here.
Jesse Johnson maintains a list of conferences in low-dimensional topology here.
I hear about many conferences from the geometry listserv here.
There are also interesting conferences (slanted towards algebraic topology, but with a broad focus) on the list here.
As far as your question of how I decide which conferences to attend, at this point in my career (on the tenure track, but not yet tenured; I started this policy when I was a postdoc) I mostly only go to conferences where I am speaking.  Sometimes I'll attend a conference where I'm not speaking if the conference has an unusually strong lineup of speakers, but I already travel far too much.
When I was a graduate student, I basically went to conferences suggested by my advisor.
A: A list at the moment maintained by myself concerning conferences related to representation theory of finite dimensional algebras:
fdlist.
A: Here are some links:
Upcoming conferences in algebraic geometry by Ravi Vakil.
Conferences on category theory. These are also often mentioned at the n-café.
A: http://www.numbertheory.org/ntw/N3.html Number theory
A: There are at least two lists of conferences in algebraic topology that I know of, one maintained by Sarah Whitehouse, and one by Niles Johnson.
A: http://www.ams.org/meetings/calendar/mathcal AMS Calender
A: In my field, commutative algebra, one goes to commalg.org for upcoming conferences, lists of practitioners, and more.
A: Conferences in General Algebra and Related Fields, maintained by Keith Kearnes.
Links to Combinatorial Conferences, maintained by Douglas B. West.
Combinatorics and related conferences, maintained by Peter Cameron.
A: Preamble: I am a graduate student at a large program, about to start a postdoc, so I can speak about what has worked for me at the (hopefully) beginning of my career.
One thing I do occasionally is to check the upcoming conferences at the NSF Mathematical Science Institutes.  These institutes tend to run many strong conferences.  Since I'm in mathematical physics, I also try to monitor the upcoming conferences at the Simons Center for Geometry and Physics and the Centre for the Quantum Geometry of Moduli Spaces, and I'm sure there are centers that I'm not aware of.
The second way I find out about workshops and conferences is via announcements forwarded to our department's mailing lists.  My adviser occasionally forwards announcements to me.  But the most important way I find out about workshops and conferences is by talking about upcoming opportunities with my peers.  Socializing at department teas is a good way to do this, and you can certainly directly ask people whose interests overlap with yours about their upcoming plans.  Moreover, as you attend conferences, you should talk to the other participants about related upcoming activities.
A: The website of the European contact and symplectic topology (CAST) network lists conferences of interest to symplectic/contact people:
http://cast.ulb.ac.be/events.php
A: Ozawa's Workshop Schedule (operator algebras, geometric/measured group theory)
A: Visit the following web sites:
atlas-conferences.com/
http://www.conference-service.com/conferences/group-theory.html
A: Concerning a somewhat niche sector (geometry of PDEs), here you may find useful announcements:
http://gdeq.org/Welcome_to_GDEq.org!
Anyway, I definitely miss a comprehensive calendar of all upcoming math events. In answer to your query, probably the best meetings I attended to I've got to know by pure chance! Which, to some extent, is exciting, but, on the other hand, also risky, since the probability to miss a potentially fruitful meeting is equally high.
From now on, I will rely also on the long list of links appearing on this page, for which I'm very thankful, but I really look forward to see some electronic system, like arXiv, where anyone is free to add an entry about his/her own event, together with a short description of it.
