There are a few answers to that question depending on what your looking for, but the absolute cheapest way to have an employee time clock that integrates with Quickbooks is to use what you likely already have in your office...A Computer.
Virtual Time Clocks are a great way to keep the costs of a new time and attendance system down, while still requiring your employees to clock in and out. You can use a dedicated PC that is centrally located that every employee can use, or you can buy a network version of software that allows you to install the virtual time clock on everyone's PC in the office.
An added benefit to Virtual Time Clocks is that employees can view their time cards (view only of course, no editing) from the current or past periods. This can help limit the number of questions that come your way, as they can look things up for themselves.
Acroprint's TimeQPlus System offers the Virtual Time Clock standard with their $129.00 software package. You also have the option of buying the network version for $199.00, allowing you to install the program on up to 50 machines.
For a $129.00 investment, Acroprints TimeQPlus System is by far the cheapest way to have a fully functional Small Business Time and Attendance System that integrates directly with Quickbooks Desktop Software.