If you want to skip the microwave, you can also cut the butter into small pieces and stack them on top of one another or flatten and pound it with a rolling pin between two sheets of parchment or wax paper. Then set the butter out at room temp to speed up the process.
You can also pour hot water into a container big enough to cover your butter, discard the water, then place it over your butter. Let it sit for around 10 minutes on your countertop, then remove the container.