If you have a spice simulator then you can get packaging data from places such as here: **broken link removed** but a Spice model from a manufacturer will normally contain the effect of the package parasitics if they are significant. Some transistor models are supplied as two parts - the semiconductor model and the package model.
Keith.
The accuracy of my answer depends on if you are designing an IC or not.
The Carsem link I gave has the parasitic capacitance/inductance for a lot of packages but it is not a "tool" - you would have to add the components manually in to the design to simulate it.