The ideal option would be to find work in his own organization. Talk to the chief, perhaps you can give additional amount of tasks that you will perform in a weekend, for a fee. Unfortunately, this is not always possible. Try also to find work in their field of activity, but in other organizations, or related fields. Work in your same profession often find programmers (part in independent projects), teachers (tutoring on weekends), staff PR-specialists of companies (classes with copywriting in free time). It helps to improve skills and to gain experience.
Sometimes a good income can bring one of your talents or your hobby. The ability to sew, knit, paint, Wallpaper glue or repairing computers can provide you stable high additional earnings. If you have no such "profitable" hobby, remember their school years. You can write term papers and to solve the control careless students in the subjects that you are familiar with. Place your ad on the student forums, in Newspapers, on the Bulletin Board or at the bus stop near the University or College.
Get an additional occupation such as hairdresser, manicurist, seamstress, massage therapist, etc. Such specialties are very much think that right now the most popular on the market and like for you. This path requires time and money, but later will provide you with a stable income. You can work on weekends, evenings or in any convenient mode.
An additional source of income, can be unskilled labor. They just can do on weekends days. Posting ads, work as a loader, a promoter or "Secret shopper", usually does not require special skills.
If you are looking for a job for the weekend online or on sites devoted to job search, sort jobs by category "part-time", "part time", "Free schedule", "Working for the weekend". This will help you to understand hundreds of sentences, selecting only those that meet your conditions.
Do not overdo it in the pursuit of money. Work without days off for a long time affects the health. Would be a shame to spend it restoring all of your additional earnings.