My outside air conditioning unit is running slowere then usual, and not cooling the house very well. I just changed the filter which was very dirty. It does not seem to be running any faster. Is there anything else I can do?

What is running slower ?

More info would help
What kind of system do you have?package or split system
Brand name?
Model numbers,2 units if you have that many
Determine what is running slower, the fan, the compressor, or maybe the indoor blower if you have one
We would be glad to try and help you
Could be as minor as just needing a capicitor

Try turning it off and waiting an hour or two than turn it back on. Maybe your indoor coil is frozen.