I'm pretty sensitive to caffeine myself, I typically stay away from any tea after about noon.  That said, I'll second Chip's suggestions to consider the houjicha or kukicha.  I was looking for the same thing, a (preferably green) tea that wouldn't keep me up at night.  The kukicha (made from tea stems) it naturally lower in caffeine than tea made from leaf, and the roasting process that results in houjicha reduces the caffeine as well.  I went all the way, bought some houji-kukicha (roasted stem tea), and I've been able to have a cup late in the evening and haven't noticed any caffeine effect.  And bonus for me, I really like the taste, I think it's great for winding down in the evening.
You might give it a try.  Of course, try it first early in the day and see if you feel any effect.  And a note -- while houjicha is technically "green tea" in that it is not oxidized, it is brown in color from the roasting, and the resulting tea liquor is brown in color, sweet and roasty.  If you're looking for a tea with more typical green tea color and flavor, you'd probably prefer the regular, unroasted kukicha.
And if that doesn't work, on to the tisanes!  As entropyembrace pointed out, nothing wrong with a good rooibos or honeybush in the evening.  Add a little vanilla soy milk and it's like dessert   
