If you are looking to save money when refilling toner, purchasing remanufactured toner cartridges is a viable option.
Compatible toner cartridges for all the main brands are available. For example, you will have little difficulty finding toner replacements for HP, Canon, IBM/Lexmark, Brother, Epson, Apple, Minolta, Samsung and Xerox products.
One caveat to remember when purchasing toner refills, however, is that each brand can have wildly different toner cartridge and bottle assemblies. Do some research to make certain the refill that is being offered fits your machine.
If you have an OPC/Toner assembly, find out if the refill has a good replacement drum. Make sure the yield of the refill replacement is not significantly less than the original cartridge.