According to an email circulated round my company, there is none.
In Europe, lead-acid batteries will be banned some time over the next few years (except for some specific applications, eg military). The reason is the nastiness of lead and sulphuric acid. I don't disagree with the toxicity issues but I don't normally feel the urge to drink out of batteries. I believe that the lead issue extends to solder, which must be lead-free from 2010 onwards.
I find the whole issue difficult to comprehend because of the immense infrastructure that exists for automotive batteries, the excellent battery recycling methods available, and the lack of a viable replacement technology. Or is there one? What are battery manufacturers doing about it? Or have I been misinformed?
John