Essential IPAQ Software
Update, June 2008: This list is absurdly out of date as I no longer use my iPAQ. I suggest you buy a new-generation mobile/cell phone instead (I use a Nokia N73, today you might choose an iPhone), it's much more flexible & convenient to carry around!
In late 2004 I purchased an iPAQ 2210, brand new, off of eBay for a very nice price. This is a quick (for a handheld!) 400Mhz processor, 64Mb of memory, and it runs Windows Mobile 2003. The base package is a nice organiser, but of course it's not as perfect as it could be.
Soon after buying the iPAQ I made sure I had enough storage with the purchase (well, swap with a mate) of a 256Mb Secure Digital card, and satisfied my inner geek by purchasing a Compact Flash GPS Receiver.
The below list is software that I deem necessary to have to make life with an iPAQ even easier. Below that is a list of cool software and games that are definately worth checking out :)
Required Software
tAgenda - This handy little program lets you see an enhanced calendar on your 'Today' screen, with very customisable options. By default I see my next 7 appointments with great detail.
DTSysView - Sort of like 'Task Manager' for Windows. Lets you see what's running in the background, switch to it, or close it. Also has a handy 'Close All' function to close applications that have hidden themselves in the background. Lastly, it provides great Memory and Battery status screens - all in front of you in one place.
AvantGo - AvantGo brings the content you want to your handheld. I've setup an account for myself and decided I'd like to view news local to me, along with a few other technical news feeds from around the world. Every time I hotsync my iPAQ, the latest content from my chosen channels is downloaded for me. Great reading for when you're sitting still for a few minutes.
Fun Software
Destinator - I've tried this on somebody elses iPAQ but haven't got it myself yet - it must be the best GPS navigation software out there. It tells you when to turn, where to go, etc. Any address I gave it, it got me to without fuss! Only thing stoping me getting it myself is the pricetag :(
Pocket MiniGolf - Nothing better to waste a few minutes than a round of minigolf :)
Age of Empires Gold Edition - If Pocket MiniGolf takes up a few minutes, this game takes your days of spare time away. So immersing - it takes me back to internet games of AoE back in my early school days. This game is so large and has so many things to explore, you can be involved for weeks.
That's about it for now, I'll add more as I come across them :)