I have a Sony Ericsson P910i; it's the bees knees. It can do almost anything a laptop can as far as the internet goes, but it is limited by its small screen. Use sites that particularly tailor their output to PDAs. I also recommend getting the Opera browser for any small screen PDA - it can format for the small screen.
I bought my P910i cheaply off Ebay (Useful if you already have a phone contract)
Access TAFs and METARS via YAWS (Yet Another Weather Service) at
http://activitae.com/airbase/mirror.htm as well as the Met Office's Form 215/214. (Activitae makes the login and page selection faster and saves wading through the numerous Met Office login screens directly.)
Also a graphic depiction of winds aloft for Europe, Africa and USA suited to the PDA is available.
World Notams too are accessible for a PDA from activitae.com. However, Notam data is by its very nature voluminous - expect to scroll down quite a lot!
A WAP version - without graphics - is available for readers with a plain vanilla phone. Also the WAP version has an ICAO code and decode function - useful if away and unsure of a destination code - at
http://activitae.com/wx.wml - this is a WAP address and will not work in most web browsers - so bookmark it to your phone.
I created YAWS for my own use, especially when away from home, after being somewhat less than satisfied by other web offerings.
Why anyone would want to pay subscriptions for data that is freely available is beyond me! But I suppose there will always be people who think paying £2 for a 20p cabbage makes it a better cabbage.
Angela
Got YAWS yet?
http://activitae.com