Anna University has more than 550 colleges affiliated to it. Many well established colleges have turned autonomous while some remain affiliated. The major difference between the two is that an autonomous college has its own syllabus but graduation certificate is still given by AU. But affiliated colleges follow the syllabus prescribed by the university. So you should aim for an autonomous college rather than an affiliated one.
Some well established colleges in TamilNadu under Anna University are
These colleges have been listed randomly and not rank-wise.