A cheap PDA strictly for cache listings... I had an M105 but it crapped out on me a few months ago so my wife got me a Zire 21. Rechargeable battery and a lot faster processor than my old Palm. I use CacheMate and paid the 7$ shareware fee, and it suits me great.

Of course, compared to some of the other cachers out there, I'm a relative newbie at only 300 caches, so I'm sure some of the seasoned vets out there have better ideas. :)