For those of you installing eclipse for the first time on Ubuntu (using the System -> Administration -> Synaptic Package manager), the Window -> Open Perspective -> Java might not appear (even under Other).
Here is what you need to do:
1. Close eclipse if you are already running it.
2. Open the Synaptic Package Manager (as above) and select the eclipse-jdt package as well.
3. Install (basically, Apply)
That'll do it! :) Start up eclipse again!