Many 401k plans offer loans to "active" participants (if you've left the plan you're probably not eligible).  These retirement loans are easy to obtain and can make sense for employees who have a secure job. 

Generally, you're allowed to borrow up to 50% of the vested balance of your plan up to $50,000.  Contact your benefits office or HR representative for details on your plan.

Here's some common 401k loan questions courtesy of 401kHelpCenter.com:

How long do I have to pay off my loan if I quit my job?

Typically, if you quit working or change employers, it is not uncommon for plans to require full repayment of a loan within 60 days of termination of employment.

Will a 401k loan appear on my credit report?

Loans from your 401k are not reported to the credit-reporting agencies, but if you are applying for a mortgage, lenders will ask you if you have such loans and they will count the loan as debt.

If I default on my loan, will the default be reported to the credit-reporting agencies?

If you default on a 401k loan, the default will not be reported to the credit-reporting agencies and it will not negatively impact your credit rating.

If I can't afford to keep making the payments on my loan, can I stop them?

Once the loan has been made, your payments will be deducted from your pay each month and you generally can't stop this process.

If I default on my loan, how will I know the amount I must report as income on my federal tax return?

You will receive a 1099 from the plan which will show you the exact amount to report. This amount will also be reported to the IRS.