The light devices usually only have 1 slot (the 4 to 5oz devices). These include the V35 and h1910 along with Toshiba e310 to e350 models. Check on their battery life too because not all of them last very long.
The heavier ones have more functions, including a CF slot or possibility of expanding to have one. For now, there's probably no wifi SD cards yet, so you'd have to give up a bit of lightness for a CF slot. These include the 6+oz devices: Toshiba e740/e750, ipaq 3700 and above (they can take expansion sleeves) and the Axim. The e740 is the lightest of these and already has wifi, so you won't have to add another card, which will be some more weight.
Of course, some new devices will be in the middle of the road. There's that new ipaq 2200 and Acer n10 which are both around 5.5oz's and will have CF.
The heavier ones have more functions, including a CF slot or possibility of expanding to have one. For now, there's probably no wifi SD cards yet, so you'd have to give up a bit of lightness for a CF slot. These include the 6+oz devices: Toshiba e740/e750, ipaq 3700 and above (they can take expansion sleeves) and the Axim. The e740 is the lightest of these and already has wifi, so you won't have to add another card, which will be some more weight.
Of course, some new devices will be in the middle of the road. There's that new ipaq 2200 and Acer n10 which are both around 5.5oz's and will have CF.