This post will serve as a repository for software I find which is fairly niche, or serves a particularly useful purpose. I'm often finding something which is useful and then can never find it again when I need it! I'm not going to include a lot of mainstream stuff, as it's readily available and documented.
Before I delve straight in, there is one website worth looking at when re-imaging a system. This site is great for installing commonly used applications and says 'no' to all the toolbars and other junk saving plenty of time if like me you perform a lot of windows installations for whatever reason.
Most of the 'standard' software you're likely to use (i.e. dropbox) won't be mentioned here. This post is meant for those fiddly things you can never find again.
WinDirStat (Windows) - Fantastic piece of software. Analyses disk usage and gives a breakdown on where your used space is actually being used. Very handy when you're running low on space and wondering what you can delete.
Duc (Linux) - Similar to above for windows, highly configurable. I've got this going as a cron job on a linux file server. Capable of generating a rather nice PNG image of a file system + much more.
TinyGrab (Cross platform) - Uploads screenshots to a remote server, allowing you to screenshot an area and then directly paste a link. This is personally my favourite way of sharing images. TinyGrab allows images to be stored on your own server if you're worried about someone else having access to your screenshots.
WinCDEmu (Windows) - ISO mounting software. There's so many of these out there but they seem to all have problems with crapware. This one works perfectly.
Netscan (Windows) - Small utility for scanning IP networks. Includes lots of features including port scanning, WoL capabilities and more. Standard 'scan' just checks if alive (often enough).
CrystalDiskMark (Windows) - Disk benchmarking software. This is my de-facto standard when testing out performance for a new SAN (for VMware) or SSD etc. Quick, easy and gets the job done.
CrystalDiskInfo (Windows) - Disk S.M.A.R.T software. Produced by the same company as above, gives a good indication of the health of a hard drive.
smcFanControl (Mac) - Fan speed control software. Handy when the automatic speed increase just doesn't do the job. Has the capability of turning your aircraft-grade aluminium mac into an aircraft-grade jet engine.
ImgBurn (Windows) - Create & burn ISO images. ImgBurn also supports creating .img files for use with other mounting software, however the ISO stuff is generally most useful.
Rufus (Windows) - 'Burn' ISO images to a USB key. Great for creating bootable installers.
Syncthing (Cross platform) - Allows you to create your own storage cloud by synchronizing files on a many-to-many basis. Comes with a nice GUI as well. URL: https://syncthing.net/