Memory Cleaner is an Open-Source and freeware, portable app to flush your memory from the system tray quickly.
Memory Cleaner uses about 5-14 MB of system memory while running, which is more than reasonable.
There is a timer that you can start or stop. Your total RAM is tracked to what's available, and you can click clean memory at any time. You can exit by clicking on the X or right-clicking the system tray icon.
One missing option is the ability to clean your memory by right-clicking on the system tray icon. We were surprised the developer hadn't considered that option.