I personally found this thread far more useful than the
Programs/Utilites & Games ~ working on the Touch HD Which is a list of all programs found to be working, not just the ones you actually use. So.. Here is a list of all the stuff I've installed so far:
Resco File Explorer
Resco Registry Editor Plugin
TomTom 7.910 (Black Theme Version with United Kingdom and Republic of Ireland 815 2024 map)
HTC HotFix for screen lag -
http://www.htc.com/www/SupportDownload.aspx?p_id=179&cat=0&dl_id=448
Gyrator 2 (Awesome for screen rotation once you've set up a few extra exclusions)
Microsoft .NET CF 3.5 (needed for various things including Gyrator 2)
CorePlayer (Good video player, works for me)
L.Sylvain Manila Calculator Skin (replacement skin for the HD calculator
FInixNOver FInix_VGA_Battery_Icons (Show battery icon with a tiny percentage. Also had to install sdkcerts.cab to make this work)
HD Tweak (Awesome tweaks for the HD)
S2U2 (Slide 2 Unlock - Latest version works perfectly and I've made a custom theme for the HD, which I might upload later)
Diamond Hologram (funky but useless 3d hologram based on the G-sensor in the phone)
Diamond Ati d3d driver (needed for the hologram app, hasn't caused me any problems yet but wise take a full backup first)
Sprite Backup (great for backing up data and applications)
Sprite Terminator (track phone if stolen/lost via GPS/SMS)
PocketPuTTY (free, open source SSH client)
Efficasoft GPRS Traffic Monitor (allows you to monitor GPRS Internet data usage both graphically and numerically)
tnyynt SD TuneUP.cab (Downloaded from this forum to make your SD card access faster)
As of this post I'm running the latest available versions of everything unless otherwise stated.