What is the value of a 1901 US half dollar?

Check on the back to see if there's a mint mark under the eagle. Numismedia lists the following approximate retail values as of 02/2010:

No mint mark (Philadelphia):

Very worn condition - $13

Moderately worn - $36

Slightly worn - $90

Almost no wear - $322

Uncirculated - $510 to $9,430 depending on quality

"O" mint mark (New Orleans):

Very worn condition - $19

Moderately worn - $74

Slightly worn - $192

Almost no wear - $703

Uncirculated - $1,440 to $24,380

"S" mint mark (San Francisco):

Very worn condition - $37

Moderately worn - $192

Slightly worn - $360

Almost no wear - $1,372

Uncirculated - $2,340 to $51,350