mo,
I use a gransfors forest axe. they are pricey now, though. I bought mine for around 70 bucks, but they're 115 now.
http://www.highlandwoodworking.com/index.asp?PageAction=VIEWPROD&ProdID=1093any decent axe with a 2 1/2lb head and 24-25" handle will work as a joinery axe.
These are pretty good axes ...
http://www.snowandnealley.com/products/axes/obsb22528.htmhere it is for 44 bucks
http://www.benmeadows.com/store/Forestry/Logging_and_Clearing/Saws_and_Axes/1409/97263/