You can also try Pavel's "greasing the groove" technique, I've been using it with donkey calf raises and with chinups for my back for a little over a week and it's working pretty well for both - the idea is to just take a weight you can hit maybe 8-10 reps with and just do 5 reps per set, sporadically through the day. I work at a gym so it's pretty easy for me to do, but you can probably tweak some at home variations of calf raises with dumbbells or something similar. I usually just do a set of each any time I pass by a calf machine or chinup bar, so I usually end up doing 20-60 reps per day depending on how busy I am. My right calf is up about 3/8" in a bit over a week, which I take to be an appreciable gain.