Chances are, if you have algae like that, something is off balance. Algae is only as bad as you allow it to become, so working to fix what causes it will help greatly.
First, what kind of light do you have? I find that incandescent lights give me algae. Consider switching to CFL's to give better, more effective light. (Try 5500-6500K daylight)
Also, how long is the light on? After about 8 hours, plants dont really use light. Any more than that probably will give you trouble. Cut back on light to avoid this.
Do you dose fertilizers? Do not over dose. If you have plants that dont really use ferts as quick as, say, stem plants, dose a bit less (ex. java fern and anubias dont need ferts in doses like a tank with anacharis)
Every time you add fertilizer, do a small water change to remove nutrients the plants havent used. Algae cant eat what it doesnt have to munch on!
Manually remove the algae as best you can.
Leaving a small amount of (controlled) algae can help prevent an outbreak. This bit is great because it keeps other algae at bay and eats what they try to-- consider getting a dark rock in the back of the tank and just let it do its own thing. Cant see it, but itll help you in time.
The only REALLY BAD algae you can get is BBA, black brush. Its scary and gross.