Glass2k!

GhostWin allows you to make any window slightly or completely transparent, and automatically adjusts the transparency level of windows that are being moved or sized so you can see what's underneath them ahead of time.

SmartSystemMenu extends system menu of all windows in the system. It appends next custom items to menu:

Moo0 WindowMenuPlus lets you have extra useful menus in every windows "system window menu". Its the menu that you can access through right-clicking on any windows title bar or taskbar button. This tool can add extra menus there such as "Keep on Top", "Transparency Adjustment", "Process Priority Adjustment", "Various Information about the Program" and so forth. Also, you can configure not to show some menus that you dont use. You can enjoy only useful menus that you want. »

PowerMenu is a small application that some extra menu items to the windows control menu in addition to the standard "Close", "Maximize", etc options. The extra menus are: Priority, Always On Top, Transparency and Minimize To Tray.

xNeat is a windows enhancement utility. With the free version you can change any windows transparency, hide it, make it always on top, send it to tray, change the process/thread priority, Shuffle the taskbar etc.

TopMenu is a functionality clone of PowerMenu, but designed to be compatible with Windows 7 and 64-bit systems.

TrayIt! - minimize to the system icon tray any program (Outlook Express, Notepad, Word, Internet Explorer, Sunbird, Thunderbird, Opera, OpenOffice etc.) and get more room in the Taskbar!

HideWin sits in the system tray and enables you to hide any top-level window with its popup tray menu or an ALT+letter hotkey that it assigns automatically. It appears to be abandonware, but it is only 13KB and still works.

Adjust the transparency of your active and inactive windows, taskbar, and desktop with this small application, which suffers from a minor performance glitch. Ghost-It places an icon on your system tray, with options to independently configure the transparency levels of your active window and inactive windows. It comes with a fade effect option and you can decide if you'd like a warning before the transparency of the taskbar and desktop are adjusted. We like that we can define a hot-key combination for activating the window under the cursor. Once you've made those choices, pick Ghost from the menu to put this freeware to work. To end the effect, select UnGhost or UnGhost All. In our tests, however, we had difficulty accessing the elements on our toolbar once its transparency faded. Despite that issue, users who often work with multiple windows should try this free tool for easy modification of windows' visibility. »