Apart from Landsat imagery, which other satellite imagery is good for land use / cover studies and can be obtained free of charge?
Which part of the world are you looking at? Archival SPOT imagery is available in many areas,but may be restricted to education and research uses. Check NASA and USGS for data. Depending on the location and scale there may be something already done that you can use for your purposes so don't reinvent the wheel if you don't have to.