Playing with Electronics Circuits

When I started this postition, one thing people asked me was to learn how electronics circuits work especially power electronics circuits. Most of it is quite confusing, so the best way to learn is normally to play with circuits, since it can be quite dangerous, I was looking for software to play with circuits which are preferably freeware. I have been introduced to PLECS which can be used in MATLAB or stand alone application unfortunatley this is a paid application. So the freeware application I have seen so far are:

1. Gecko This has a free Java applet but the full one is not free.
2. Circuit Simulation Applet Not sure this has the full range of componets ie it doesn't have a IGBT, still it looks good
3. 5Spice is a graphic design of circuits that you will have to buy after 30 days, I think However it is related to spice
4. Spice this is a text based way of doing circuits, there is many application who have added graphical displays to run spice, normally this isn't for free.

If you do manage to find any electronic/electric circuit websites/applications please post them in the comments.