Yes - Perfectly possible. In fact, that's exactly what I am doing right now.
One IDE interface (i.e., cable) supports two devices - one must be the master, the other must be the slave. So, you'll need two IDE cables.
The first harddisk should be the master on the first IDE interface, for the most trouble-free operation; for the same reason, the second harddisk should be its slave.
The most natural thing to do, then, is to configure the third disk as the master on the second IDE interface; I have my DVD recorder as its slave.
If your computer supports it, and if you have an appropriate cable, you can jumper both devices on the cable as "Cable Select." The device that is connected to the end of the cable will, then, magically become the master, and the device that sits on the middle connector will be the slave. (An "appropriate cable" would have 80 wires, instead of 40, and you can identify it by the colours of its connectors: one blue, one grey, and one black.)
If you have an older cable (I think "IDE-33" is what they are called - note, however, that these won't provide the top-level performance that modern IDE interfaces support), or if you have an older computer that doesn't support "Cable Select," or even if you just prefer it that way, then you can jumper one device as the master, and the other one on the same cable as slave; in that case, it doesn't matter on which connector they sit (i.e., "master" and "slave" jumpers override the cable select positions).
Do remember to either jumper both devices on one cable as "Cable Select," or configure one device as "master" and the other one as "slave." You may, however, use the "Cable Select" option on one cable, and the "Master vs. Slave" configuration on the other one, without problems.
Personally, I'm using "Cable Select" on both of my IDE interfaces.