NoSleep! is a simple app that will enable you to temporarily keep your machine awake.
NoSleep! resides in the systray, and with one-click, you can deactivate the screen saver and sleep/standby. You have three options to choose from; Preserve State, Emulate Keyboard and Display Internet Time. They can be accessed by right-clicking the icon and selecting Settings.
It isn't the most complex app, but that is the point. NoSleep! is meant to be as simple as possible to configure and use.