Si:
It may be an old technology, but I have come to the conclusion that I like using lead-acid batteries. They are a lot less fussy about how they are charged than NiMh's or LiPos. I used them in my solar radio (Dr. Monk's DIY Electronics Blog: Arduino Solar Radio) mainly because they are quite happy being trickle-charged with a current that frequently varies by a factor of 10 depending on the weather (I live in England).
Unfortunately lead acid batteries cannot tolerate over-discharge, even for short periods, and they lose capacity and lifetime if you let them fully discharge. NiMH are much more resistant to this I think - so it rather depends on whether you expect the battery to become fully discharged. Lead acid should be stored fully charged and regularly topped-up in storage.