Benefit options for retiring widow/widower

Social Security survivors benefits can be paid to a widow with full benefits at full retirement age, or reduced benefits as early as age 60.

If you are collecting survivors benefits, you can switch to your own retirement benefits (assuming you are eligible and your retirement rate is higher than the widow's rate) as early as age 62.

Note that if you work and receive retirement benefits, your benefits will be reduced for amounts earned above a certain level. If you were born January 2, 1943, through January 1, 1955, then your full retirement age for retirement insurance benefits is 66. If you are younger than full retirement age during all of 2009, Social Security will deduct $1 from your benefits for each $2 you earned above $14,160.

See here for details :
http://www.ssa.gov/ww&os2.htm
http://www.ssa.gov/pubs/10069.html
http://www.ssa.gov/estimator/