I used a few different things, mostly what I had in my cupboard. So, fenugreek, amaranth, the quinoa never sprouted, cumin, and then the 'purpose bought' covers of a couple different varieties of clover, and now I'm drawing a blank on the other stuff. I get the fenugreek in bulk at bulkfoods.com. I use a little cordless hedge trimmer to chop & drop it during the season, otherwise it grows up into the cannabis and that's caused a problem so I keep it below the canopy. The crops do have to get sufficient light to grow well, I had one plant that shaded everything out entirely, but that plant was growing very vigorously and so was able to shade and penetrate her own soil bed just fine. I feel the cover crops do better in a bed or mound scenario for that reason.
I loved the results in that I was able to keep watering down, didn't see all the run-off through the beds (I bring in top soil and plant either in Smart Pots, ghetto SPs or raised beds because we're on very extremely heavy clay here) that I typically see when trying to keep the soil for my cannabis moist enough. I hope that sentence made sense.