Trip, sunder, and disarm replace a single melee attack and thus can be interspersed in any order in multiple attack routines, as part of a flurry of blows, and as an attack of opportunity. This is clear from the descriptions of the maneuvers in the SRD.
Of course, these may provoke attacks of opportunity of their own, and other feats and weapons you may have might affect number of attacks and bonuses thereto. In our pirate campaign just today, we had a monk consistently tripping first in his flurries to benefit from the lowered AC of the prone opponent, and a big barbarian who would use his lower-to-hit second attack on disarms since he figured on the off chance he connects it might as well mess with the opponent more than just some damage. Make sure and read the prone rules and other related areas to understand how all this will work.