ESL-2 to EML-1
Martin Lo of JPL gave a nice talk on this at last year's ISDC meeting in San Jose. The various L points in Earth's neighborhood are connected by chaotic orbits that require essentially no delta-v to go from one to another; you just need a little boost to get on the right orbit, and some control from then on - travel time would be months to a couple of years, generally. So for servicing telescopes at ESL-2, a human-tended station at EML-1 would be perfect.