Stealth Storage
Stealth Storage is a small and powerful file encryption tool. It encrypts files on-the-fly using well-known strong ciphers like BLOWFISH, RIJNDAEL etc. It is totaly invisible when installed. Nobody will even notice there are encrypted files on a computer.
http://www.stealth-storage.com/stealth-storage.exe - 433Kb - Download - Screenshot

Computer Monitor Keylogger
Secretly monitor all activity on your computer, capturing keystrokes, programs, internet explorer websites and screenshots. Completely invisible and easy to use, all information captured is stored in an encrypted log file. The log file can be sent secretly at scheduled intervals to any... Capture programs used Capture websites in Internet Explorer Capture screenshots Encrypted log file Secretly email log files Invisible "Stealth Mode" Unique playback mode lets you view captured keystrokes/programs/webpages/screenshots in real time Run silently at startup Auto-capture at startup Does not...
http://www.rebrandsoftware.com/demodownload.asp?id=19 - 3Mb - Download - Screenshot

CowSpy
CowSpy idea: Many programmers have been in a situation where they see another program window and they think how is that GUI build up. Or perhaps th programmer is trying to write a program that interfaces with a specific program. For instance but an extra button in another program. ... * Make windows visible and invisible or just one component off a window. ... * Option to see all the windows even the invisible ones. ... * See the Parent child structure between windows their childwindows and components like buttons and labels.
http://www.nakencow.tk/cowspydownload.php - 79Kb - Download - Screenshot

EndTask Basic
The Basic edition of the End Task family includes the full featured Pop-up Blocker and a powerful Task Manager. Unlike other pop-up blockers, ours won't kill pop-up windows you want. Our blocker hides pop-ups and just shows information about them. With a simple mouse hover you can take a peek... The technology is invisible to sites that try to detect and foil blockers. ... Take a direct look at the numerous "processes" running on your machine (including the invisible/background ones) and how they are using your computer's bandwidth, memory, and much more.
http://www.endtaskpro.com/download/EndTaskBasic.exe - 1Mb - Download - Screenshot

Mini Key Log
Mini Key Log makes it possible for you to monitor and record user activities unnoticed and store this in log-files. This log-files are fully searchable for specifically keywords and sorted after user names and time. The monitoring process is completely invisible and easy to use.
http://www.blue-series.de/download/MiniKeyLog.exe - 555Kb - Download - Screenshot

PC Agent
PC Agent makes it possible for you to monitor and record user activities unnoticed and store this in log-files. This log-files are fully searchable for specific keywords and can be send compressed and encrypted to a shared resource in the network or to a predefined e-mail address. ... The monitoring process is completely invisible and easy to use.
http://www.blue-series.de/download/PCagent.exe - 782Kb - Download - Screenshot

Oban MultiDesk Expert
Real powerful multiple desktop management tool, Anyone may well find it a welcome, low-overhead way to expand their work spaces. It provide user industry-lead solution with following features: 1. Takes up very little resources , and it doesn't slow performance. ... It also allow a window or desktop Icon to be made 'invisible' meaning the responding items will be invisible on all of the virtual desktop. ... They are hot-keyed to the ANY YOU WANTED keys for easy desktop switching. ... 5. ... You can easily change their state using mouse or pop up menu.
http://www.obantech.com/download.php?file=MultiDesk-Expert.exe - 2Mb - Download

MatrixShow ActiveX
Shows the content of matrices, that are given as two-dimensional arrays. This can be done both in runtime mode and in design mode. The element itself is invisible. It shows a form to give out the matrix content. The matrix display for example serves debugging purposes.
http://www.sensalgo.com/downloads/saobusax.zip - 2Mb - Download - Screenshot

HideIt!
HideIt! is your personal data key. With its help, you can easily and reliably hide any files on your home or work PC from outsiders, and unauthorized users. Nobody except you can get access to your hidden folders and files. No one will ever know that you made some of your files invisible to... creates guarded and invisible space on your hard drive. ... You can still use or modify these files without any changes and it is always up to you which file you would like to use. ... It does not matter what kind of file you would like to use as your data hiding cover, it can be a simple text...
http://www.guard-software.com/products/hideit/hideit_setup.zip - 708Kb - Download - Screenshot

Family Keylogger
Family Keylogger - this is the best choice, if you want to know what others are doing on your own computer while you are not at home (or office). Install Family Keylogger, set options "Start in hidden mode" and "Hide in task list", so that it makes itself invisible to anyone. ... Family Keylogger - You have the right to Know! ... After you return, you can just press keystroke to unhide.
http://www.spyarsenal.com/familykeylogger/familykeylogger.zip - 520Kb - Download - Screenshot