I recommend the Dell Axim x30 or x50. The x50 has a lot more power, a better screen (QVGA?), built in WiFi and bluetooth. My x30 which is cheaper, but it still fine. My x30 didnt have WiFi, so I had to buy a SDIO card. Of course there is an x30 with WiFi. Ive used both and they are both solid devices. You can also get a refurbished one from Dell at a decent price (my x30 was only $130 from the Dell website).

From what I hear the HP iPaq's are good, but I havent used one in a long time. Also the Asus MyPal looks like a good PPC also.

Also if you are going to plan on using Skype on a PPC, then you will need a PPC with alteast a 400mhz processor (which rules out the x30), as it gets somewhat choppy.