Signal generator is handy tool in lab. But in some areas of electronics it’s not so important to deserve money to be spent on. And so you can always rely on your skills and build your own DDS signal generator out of few common parts.
Tuomas built an AD9833 based DDS signal generator. This is a specialized chip from Analog Devices which is capable of generating sine, triangle and square waves at frequencies from 0.01Hz to 3MHz. It has to be controlled using SPI interface. This is where AT90USB162 comes in. It takes care of giving commands to DDS chip, and talk to PC using USB interface. He has written a handy GUI using Python where signal parameters can be easily changed.