I have some seed left over from germinating Paulownia tomentosa. This tree is a rapid grower, and may be considered potentially invasive in some areas but seems to behave itself here. You can see my posting on its growth rate here:
http://nargs.org/smf/index.php?topic=1081.msg22308#msg22308
The seeds germinate readily, surface sown in sun. I use the clear plastic clamshell containers to start them in their own little greenhouse, on a bright windowsill, like this: