Speaking for myself, I never appreciated dummy loads until I needed one. And if you are building DIY circuits or do research around electronics, you will definitely need one. Definitely.
Here is a 30W Adjustable Electrical Load from Electro-Labs able to sink up to 5 Amperes of current continuously.
|This board will come to aid when you need to draw an exact amount of current from a supply. For instance to learn the current rating of a power supply, measure the heat dissipated on a circuit element, discharge a battery etc.|
The circuit is built around the IRF3710 MOSFET, 30W, 5A and 100V are the limiting parameters of the load"
A built in ammeter shows the actual current flowing through the MOSFET. The current is set using a multi-turn variable resistor for precise set.
All the details of this make are found here.