Paint companies have caught on and we now have plenty of zero VOC paints to choose from (See a roundup of them here). But there are plenty more ways than paint selection to green your painting.
The Drop Cloth
If you paint every year, you may consider reusable drop cloths. Consider using old curtains, or fabric before purchasing a new canvas one. For the renter or occasional painter, you may want a disposable one but be sure to choose from one that is made from recycled materials, or at a minimum, that is recyclable itself like this paper drop cloth.
Green Caulk and Adhesion:
These products from Titebond (makers of quality glue products) have eliminated the solvents in their green line to improve indoor air quality, without giving up the strength they're known for. They also come in post-consumer recycled tubes.
Removing the Old Paint
If you're painting an old window sash, door, or previously painted piece of furniture, it's sometimes necessary to remove the old paint before apply the new. Instead of traditional strippers that have harsh chemicals, this soy gel stripper, is a much less toxic alternative.
The Paint Tray:
Most latex paints will clump together at the bottom of a paint tray, allowing you to peal them off in a couple pieces. Alternately, if you let them dry, you can pour fresh paint over it without it contaminating your color. If you must have the convenience of a paint tray liner however, here is a biodegradable option to make that convenience more environmentally friendly:
Whether you're painting furniture, or simply cutting in, a paint brush is a necessary tool. Instead of purchasing disposable brushes, invest in a high quality brush that will last a lifetime. I swear by Purdy brushes, which I have been using ever since I worked at a cabinet shop. Wooster also makes fine brushes. Be sure you get all the paint out of the brush after every use (for latex paints, all it takes is water).
Using zero VOC paint is great, but for increased coverage and a better finish, using a primer is vital. Be sure to choose a zero VOC primer to match your paint.
And finally, for making the best of that zero VOC paint, see this how-to on maximizing your new color.