We are paid bi-monthly. My company has a posted payroll date of 12/19/07 for the previous period. Today no one has received their direct deposits nor have the received their payroll checks. What can be done?

Call HR and ask what's going on?

If the paychecks don't come through, workers can file a wage claim with the state:

http://www.dir.ca.gov/dlse/HowToFileWageClaim.htm

Ca. labor code 204:All wages earned by any person in any employment are due and payable twice during each calendar month, on days designated in advance by the employer as the regular paydays. Labor performed between the 1st and 15th days, inclusive, of any calendar month shall be paid for between the 16th and the 26th day of the month during which the labor was performed, and labor performed between the 16th and the last day, inclusive, of any calendar month, shall be paid for between the 1st and 10th day of the following month. However, salaries of executive, administrative, and professional employees of employers covered by the Fair Labor Standards Act, as set forth pursuant to Section 13(a)(1) of the Fair Labor Standards Act, as amended through March 1, 1969, in Part 541 of Title 29 of the Code of Federal Regulations, as that part now reads or may be amended to read at any time hereafter, may be paid once a month on or before the 26th day of the month during which the labor was performed if the entire month's salaries, including the unearned portion between the date of payment and the last day of the month, are paid at that time. Notwithstanding any other provision of this section, all wages earned for labor in excess of the normal work period shall be paid no later than the payday for the next regular payroll period.

If you don't get your paychecks, file a claim (as suggested) with the Ca. DLSE.

And, just to clarify, that would be semi-monthly (twice a month), not bi-monthly (once every two months). Bi-monthly is not a legal pay frequency.