I am a 62 yr old female. If I take my social security early [spousal benefits] how will that effect our taxes if my husband keeps working?

The worksheet in the 2008 Form 1040 instructions is the best way to determine what part of your SS is taxable.
It is on page 27 and copied below:

Social Security Benefits Worksheet—Lines 20a and 20b Keep for Your Records
Form 1040—Lines 20a and 20b
Before you begin:  Complete Form 1040, lines 21 and 23 through 32, if they apply to you.
 Figure any write-in adjustments to be entered on the dotted line next to line 36 (see the
Instructions for line 36 on page 34).
 If you are married filing separately and you lived apart from your spouse for all of 2008,
Enter “D” to the right of the word “benefits” on line 20a. If you do not, you may get a math
Error notice from the IRS.
 Be sure you have read the Exception on page 26 to see if you can use this worksheet
Instead of a publication to find out if any of your benefits are taxable.
1. Enter the total amount from box 5 of all your Forms SSA-1099 and
Forms RRB-1099. Also, enter this amount on Form 1040, line 20a.. . 1.
2. Enter one-half of line 1.. . 2.
3. Enter the total of the amounts from Form 1040, lines 7, 8a, 9a, 10 through 14, 15b, 16b, 17
Through 19, and 21.. . 3.
4. Enter the amount, if any, from Form 1040, line 8b.. . 4.
5. Add lines 2, 3, and 4.. . 5.
6. Enter the total of the amounts from Form 1040, lines 23 through 32, plus any write-in
Adjustments you entered on the dotted line next to line 36.. . 6.
7. Is the amount on line 6 less than the amount on line 5?
No. STOP None of your social security benefits are taxable. Enter -0- on Form 1040, line
20b.
Yes. Subtract line 6 from line 5.. . 7.
8. If you are:
• Married filing jointly, enter $32,000
• Single, head of household, qualifying widow(er), or married filing
Separately and you lived apart from your spouse for all of 2008,
Enter $25,000 }.. . 8.
• Married filing separately and you lived with your spouse at any time
In 2008, skip lines 8 through 15; multiply line 7 by 85% (.85) and
Enter the result on line 16. Then go to line 17
9. Is the amount on line 8 less than the amount on line 7?
No. STOP None of your social security benefits are taxable. Enter -0- on Form 1040, line
20b. If you are married filing separately and you lived apart from your spouse
For all of 2008, be sure you entered “D” to the right of the word “benefits” on
Line 20a.
Yes. Subtract line 8 from line 7.. . 9.
10. Enter: $12,000 if married filing jointly; $9,000 if single, head of household, qualifying
Widow(er), or married filing separately and you lived apart from your spouse for all of 2008. . 10.
11. Subtract line 10 from line 9. If zero or less, enter -0-.. . 11.
12. Enter the smaller of line 9 or line 10.. . 12.
13. Enter one-half of line 12.. . 13.
14. Enter the smaller of line 2 or line 13.. . 14.
15. Multiply line 11 by 85% (.85). If line 11 is zero, enter -0-.. . 15.
16. Add lines 14 and 15.. . 16.
17. Multiply line 1 by 85% (.85).. . 17.
18. Taxable social security benefits. Enter the smaller of line 16 or line 17. Also enter this amount
On Form 1040, line 20b.. . 18.
If any of your benefits are taxable for 2008 and they include a lump-sum benefit payment that was for an earlier
Year, you may be able to reduce the taxable amount. See Pub. 915 for details.
TIP
- 27 - Need more information or forms? See page

I apologize for the less than perfect form. You can see it in your 2008 1040 instructions, page 27 or on the IRS website if you select form 1040 instructions.

Your social security benefits including social security disability benefits (excluding SSI payments) may be taxable, if the total of one-half of your benefits, plus all your other income including tax-exempt interest is more than the base amount of $32,000 if you are married filing jointly.
Read Social Security Income and Disability Benefits Your U.S. Tax Return: The U.S. Income Tax Topics 1 (http://taxipay.blogspot.com/2008/08/us-income-tax-topics-1.html)