These are some websites I've found interesting/helpful in my academic life so far.  Note that I wanted and attained a liberal arts college teaching job, so my job advice sites tend to be in that vein. This is not intended to be a comprehensive list.

General interest

Of course our webpage contains many discussions on the life of a
mathematician.

    http://concerns.youngmath.net

PhDs.org collects articles and is mainly aimed at people in the
sciences, whether they are undergrads, in graduate school or in
academia. Quite a few of the rest of the links are from there.

    http://www.phds.org

This is the listings of the 2003 Chataqua programs, which consists of
summer programs in many fields which are free for participants (mostly
professors)

    http://www.engrng.pitt.edu/~chautauq/

Postdoctorate.net Features Archive.  Articles about teaching and
getting jobs in the sciences. I particularly liked "How to get a job
at a primarily undergraduate institution" by Malcom Campbell at
Davidson College.

    http://www.postdoctorate.net/FeatureArchive.html

For undergrads and grad students

Undergraduate Math majors links from the AMS website. Lots are about
REUs and graduate school, but there are some more general ones as well.

    http://www.ams.org/employment/undergrad.html

Questions to ask when thinking about about pursuing a Ph.D.  This site
had some general advice and specific advice for math as well.

    http://www.phd-survey.org/advice/advice.htm

The 2000 National Doctoral Program Survey.  This is the results from a
survey of graduate students rating their schools.  Individual
departments have ratings if there were enough responses.

    http://survey.nagps.org/index.php

Customize rankings of graduate schools based on your criteria.

    http://www.phds.org/rankings/

For those on the job market

The AMS list of job advice links

    http://www.ams.org/employment/job-articles.html

Job Interview Advice from Tom Hull at Merrimack College

    http://chasm.merrimack.edu/~thull/job/jobint.html

How to make the First Cut by Paul Humke at St. Olaf College

    http://www.stolaf.edu/people/humke/winnow.html

Tips for a Massive Academic Job Search by Ellen Spertus.  A thorough
description of a two body problem job search in computer science with
many useful links.

    http://www.mills.edu/ACAD_INFO/MCS/SPERTUS/job-search/job.html

Project NExT is a program through the MAA for new PhDs. It good thing
to apply for in your first or second year on the job (even if you are
in a temporary job, they may be willing to foot the bill)  I have found
it quite useful.

    http://archives.math.utk.edu/projnext/