We have a constant systems homogenizer that we use routinely as a service for researchers here at UGA. It is really easy to use and gets up to high pressure (40k psi) so you can lyse plant cells or other difficult to lyse cell types.  You just pour/pump your resuspended cells, as low as 25mL, into the inlet, setup parameters (usually once) and hit the start button.  The lysed cells will exit the outlet line.  We usually have 2 cups to catch the outlet and we recycle 3-6 times. The unit will automatically shutoff when it runs out of liquid.  Below is a link to the website for the company with a video.  For greater than 1L of cells we have a Niro-Soavi high pressure homogenizer (second link) that I recommend.

http://www.nirosoavi.com/products/Ariete_NS2006.asp