Whether you need supplies, patterns or ideas, getting them for free can be helpful, especially if you want to use the funds you do have for something big, like a field trip. You can use bartering, service trade, donations, craft and DIY websites and even your local library to get the supplies you need and learn of new projects. Check out services like Freecycle and websites like Creativity Portal and Instructables.
Finding traditional school art supplies for free can be hard, although you may be able to get them donated through a recycling group like Freecycle. A unique alternative that can also be useful for teaching kids about recycling and ecology is to find recyclable material to make "found object" art. Old toys can be used to create a new mobile, while leftover spools of wire can be used to make wire sculptures. Be creative and visit recycling centers, scrap yards or simply watch where you walk for interesting things lying on the ground. Have students collect clean plastic bowls, cardboard boxes, wrapping paper and other things that may be useful in the classroom.
Coming up with educational projects can be difficult, particularly if you are a regular teacher trying to make up for a lack of art education. Try to tie art projects in with what the class is currently learning. For example, have students make paper costumes based on their study of Egyptian gods. Art can even be used to help teach math and geometry. Other alternatives are to look in your local library for books of art projects. Online you can find hundreds of projects, sometimes categorized by subject on teacher websites, but a better option may be upcycled "green" crafts websites like Instructables. These websites focus on recycling and sustainability, so many of the projects are free or very low cost and done using what some might consider "trash."
Use image editing software to edit an image so it only has a few colors. Have students collect foil wrappers by the color and cut them up into small squares. Draw the image on a large paper and have the students fill in each area of color with glued in foil bits to make a cool collage.
Have students bring in a string of Christmas lights and as many 20-oz. clear plastic soda bottles as they can. Cut the bottoms off the bottles --save them for paint mixing cups---and help them attach a bottle over each tiny light. Use markers to draw designs on each bottle for a cool stained glass effect.