Unless making a full hydrodynamic model, it might be hard to answer your question...
Do you need a 3D simulation, just a 2D one?
Do you need to show liquid falling, dripping, streaming along an incline, flowing on a surface (eg. a maze...)?

In any case, perhaps particle simulation could do the job. I would look toward traer.physics, it might be usable for that.

Hi Punchik, you can go for a particle based approach like the link antiplastik sent, or you can go for a cell based approach. I went down the latter route and followed the instructions here http://www.dgp.toronto.edu/people/stam/reality/Research/pdf/GDC03.pdf

with additional help from here
http://www.mikeash.com/?page=pyblog/fluid-simulation-for-dummies.html
(though the latter solves it in 3D which was unnecessary for my needs).
My results are here
http://www.memo.tv/psychedelic_fluids_and_particles_with_processing

I wanted to release the code for the fluid system, but I want to clean it up first and haven't had a chance yet! But i'm sure those links will be quite helpful...