The 2011 401(k) plan contribution limits are unchanged from 2010. For that matter, they are unchanged vs. 2009.
2011 401(k) Contribution Limits
The 2010 401(k) contribution limit remains $16,500. If you reach age 50 by December 31, 2011, you can save $5,500 in your 401(k), for total 401(k) savings of $22,000. This 2011 catch-up contribution is also unchanged for the last two years. Interestingly, the maximum you can contribute to a 401(k) plan is unaffected by total income, marital status, or participation in a regular IRA or Roth IRA.
Note that both the limits also apply to 403(b) and Section 457 plans.
Depending on any restrictions placed on your plan by your employer, your individual contribution limit might ultimately be somewhat lower. Possible causes include a cap on the percentage of pay you are eligible to contribute and your employer not yet allowing for catch-up contributions.
If you can afford it, contributing up to the limit is a great idea, since a 401(k) plan is one of the best ways to save for retirement.