Speed of tectonic plate movement I'm doing some research about tectonic plates and at which speeds they move and in which directions, because I'm writing a program to simulate the movement of the tectonic plates and also calculate where they were at previous times and where they will be at some time in the future.

For this reason, I'm trying to find some good information about the speeds of the movement of the tectonic plates over the years and in which direction they were moving. I found one set of estimates here but I'm not exactly sure how accurate they are. I also found estimates on the Wikipedia pages for each of the plates, but it doesn't agree with the first estimate and I also want to know how significantly these speeds are changing over time (I assume the movement of the plates is not linear).

Finally, the first site doesn't give in which direction they are moving and Wikipedia does, but I don't quite understand it - it says, for example "west relative to the African plate", and I'm not sure what exactly that means.

Any help would be appreciated here. Thanks!
Check out the USGS seismic data maps for each area of interest. For example, 
http://walrus.wr.usgs.gov/tsunami/samoa09/ 
gives you the relative speed and direction of the Pacific Plate relative to the Fiji-Tonga-Australian plate. The directional arrow on Figure 2 gives the mean relative motion in mm/year.