An easy one! This variable DC power supply kit has been on the shelf for a couple of years. It took all of half an hour to assemble. Another testament to my powers of procrastination!
I bought it originally to use as a test-bench PS. It will come in very handy for projects that require something other than the standard 12 VDC so readily available in one's radio shack. It will take up to 30V AC or DC and give you a range from around 1 VDC to 2 or 3 volts higher than the input.
It took me more time to locate and modify a right-sized enclosure and mount the kit inside that it took to assemble the board itself. In the pic it is using a small 9 VDC wall wart as input and the adjustment pot is set to maximum (min. voltage was 1.25V). The kit as-is can put out about 1.5 amps, but by simply replacing the voltage regulator (an LM317) with a beefier regulator, such as the LM338, the output can be boosted to 5A. An LM338 is on the way. For what I paid for this kit I think you can do better on eBay and get a fan-cooled LM338, too.
I now feel ready to tackle the SoftRock SDR kit with its many tiny parts. I've been reviewing SMT soldering tutorials on YouTube, such as this one (or maybe even better and definitely shorter, this one) in preparation for the next project, the SoftRock Lite II SDR receiver. Though the kit can be configured for any HF band, it can only be built for one. I still haven't decided which band to select.