I was reading the homepower email I got the other day and in it they shared a company that is selling lithium battery packs for solar PV setups. The prices are pretty steep, but the cycle life is vastly longer than lead. At 80% DOD, they claim ~500 cycles for lead, and 2000 for their lithium pack. At 60% they claim 4000 cycles vs maybe 700-800 with lead. They offer 12V, 24V, and 48V packs with Ah ratings from 180 to 1000. They come in a nice metal enclosure with a battery management system, and probably best of all they are made to work with inverters designed for lead acid systems, so its pretty much plug and play.
You can check them out here:
Nickel-Iron NiFe batteries by Iron Edison