Lately my speed has been increasing quite a bit even though I haven't even been trying specifically to work on speed! Guess i'm just lucky, haha. Well, i've been practicing a lot lately. And i'm not playing any music that is specifically "fast" but the "amor dios" tremolo piece by barrios certainly requires fast picking. I think working on tremolo is a good "oblique strategy" for increasing speed.
The things i've done lately that seem to help the most with my speed, though, are....
Playing arpeggio studies. The melodic kind, not like Giuliani arpeggios. I play diatonic seventh chords on all the scale degrees in the full range of a 2 octave scale in the same position (sometimes moving up or down one fret). When I started doing this regularly it increased the fluency of my right hand quite a bit and made scales feel much smoother.
Thinking of moving my fingers in "chunks" as scott tenant advises. Feeling groups of two or three fingers instead of one at a time.
AMI scales have helped my right hand a lot too. I feel like it really evens out my right hand to do a lot of AMI scale practice. I also play my scales with repeated notes... play each note one, two, three, and four times.
I can't say what exactly helped with my speed because I was never thinking about it specifically. But I think, like everyone is saying, focusing on evenness and precision, without specifically thinking so much about speed, makes a big difference.