The HP Mini-Notes have a really nice keyboard on them ...
HP Compaq 2133 Mini-Note PC (KX870AT) specifications - HP Products and Services Products
or, if you want Windows XP instead of Vista ...
HP Compaq 2133 Mini-Note PC (KR939UT) specifications - HP Products and Services Products
Both are slightly over the $700 budget ($720 and $750 respectively). Technically, you can get ones below $700, but they lack Bluetooth, CPU speed, RAM, etc.
List of models -
HP 2133 Mini-Note PC Products and Services
We have one model (the first one I listed) at Staples if you wanted to try out the keyboard ...