Dough is a free envelope budgeting application. It's designed to be both simple and attractive whilst being very effective at helping you keep in control of your spending.
Dough is available as free software under the GNU General Public License. There are no limitations or restrictions of any kind and the source code is available for download and modification. Feel free to peruse the code and submit any bug fixes.
Dough is available for Windows and Linux. A Mac port IS possible, but I don't have the facilities to do it myself. If someone could please build and package Dough for Mac, please contact me.