Like its print sibling, Kiplinger.com offers sensible advice and columns across the whole spectrum of personal finance. You'll find helpful 401(k) articles such as "Don't Leave Your 401(k) Behind," "Bankrupt Bosses Can't Touch 401(k)s," and "Max Out Your 401(k)." Use the site's calculators to discover things like "Am I saving enough for retirement," and "How do 401(k) salary deductions affect my take-home pay?" Click the community tab for forums and feedback from the site's active users on topics ranging from a comparison between 401(k)s and 403(b)s to how to handle a non-spouse 401(k) inheiritance.

BEST: The calculators.

WORST: You'll waste a lot of time unearthing the 401(k) information that is buried on the site.