The All Sky Automated Survey (ASAS) is a low-cost project dedicated to constant photometric monitoring of the whole available sky, which is approximately 10^7 stars brighter than 14 magnitude. The project’s ultimate goal is detection and investigation of of any kind of the photometric variability. One of the main objectives of ASAS is to find and catalogue variable stars.
ASAS is a vital ongoing survey of southern variables brighter than about V=12.5. Go here to find out what just about any southern variable has been doing for the last five years. Sky coverage is about once every 3 days. A convenient way to find ASAS data on a star is to look it up first in VSX and select External Links > ASAS Light Curve in the Detail Sheet.
There is an important tutorial on using ASAS data at https://sites.google.com/site/aavsosequenceteam/asas-tutorial.