If the last organiser you saw was a Psion Series 3 - much loved for its handy size and a battery life measured in months - you'll be pleased to know this classic unit is still with us. It's been restyled as the Series 3mx (pound;200), but is still held like a hamburger, typing with two thumbs. That all changed with the Psion Series 5mx (pound;390) with a keyboard that makes typing on train journeys easy. Battery life is brilliant at 20 hours and it has office-type software, such as a spreadsheet.
Psion's competition comes from Windows CE machines, most of which have gained colour screens like the Hewlett Packard Jornada 680 (pound;570) and the LG Phenom Express (pound;540). Not only do both do the basics of connecting to a desktop, they connect to networks (if suited), the Internet and email with their built-in modems. Though a tad big for the pocket, both have good keyboards with the Phenom offering a very respectable typing tool.
Larger still, but still less than a laptop, are the Psion Series 7 colour version (pound;650) and the ewlett Packard Jornada 680 (pound;570). With more than a day's battery life, and the instant switch-on of a portable, both fit in a middle ground and have the keyboard and screen space a busy person needs. As its makers say, you can fill those idle moments now charmingly called "downtime".
Forsake the keyboard and you go smaller. There are palm-size devices with a diary that almost fit in a shirt pocket and on which you write on the screen with a stylus. With the market-leading Palm III (pound;170) and Palm V from 3COM, you'd best enter most of the info on your desktop machine, adding short diary entries when away from base. Both are easy to carry, quick to learn and the batteries last a few weeks.
If you want features the Palm V (pound;250) has lots together with looks that compare well with Casio's Cassiopeia E105 (pound;420). The Casio has a bright colour screen, voice recorder and six-hour battery life - good for a high-power device. Nice to use, it shows its fashion sense by playing music and video. As a Windows CE machine, it's also sold in a package for logging data in experiments. Which points to some classic buying advice: as well as knowing what you want a pocket machine for, it also helps to know what you don't need it for.