Memory Map runs on a pocket/pc PDA but is a pretty naff job. It displays the CAA charts OK if used on a 640x480 PDA like the HP4700, useless on anything less.
CoPilot is available for the Palm; I used it on that myself but it is a very US-centred product with many UK airfields missing. It does W&B very nicely.
Oziexplorer runs very nicely on a HP4700 too, but you have to obtain the scanned maps somehow.
There isn't much else. PocketFMS is worth a look although the database is something I would personally not trust that much (user compiled).