Wimoweh is a menu-bar application that allows you to have better control over how your Mac sleeps.

Features

• Shows which apps are preventing your Mac from sleeping and why.
• Stay awake based on average CPU usage over time.
• Stay awake based on available services on your local network
• Set-up a countdown to keep your Mac awake for a certain amount of time
• Allows you to always stay awake when certain applications are running and automatically sleep when they've finished. This is great for apps that OS X seems to 'ignore' even though they're working or if you're waiting for a lengthy job to finish and want the Mac to sleep afterwards.
• And of course, you can just keep your Mac awake indefinitely.