If you are single, with no dependents, standard deduction, no other deductions or credits - and have $26,000 income from wages - your 2009 federal tax liability would be $2080 minus $400 (Making work pay credit) = $1680.
Your actual tax liability would be less because of income tax withholding - If the amount withheld was $780 - please check on your W-2 from box 2 - that you will owe additional $900.
Similar verification should be done for your state.
Let me know if you need any help or our estimations should be adjusted.
$1000 from freelance income - is classified as self-employment income. You generally should deduct qualified expenses and only NET self-employment income will be a subject of income and self-employment taxes.
Assuming $1000 is your net income (in additional to $25,000 of wages) your income taxes would be $2069, plus self-employment taxes - $142, minus make work pay credit $400 minus $949 withholding - total additional tax liability $962 - so far your calculations seems as correct.
CASDI stands for "California State Disability Insurance" - it is deducted on your California tax return - but generally is not used on the federal tax return unless you itemize.
Let me know if you need any help.