Best time slot for listeners is gonna be Saturday evening between 6 and 9 surely? 11pm most normal people are out on the town... particularly for the dancier stuff.
Have any of you guys been out promoting your shows on other forums? GYBO, mashuptown, other music forums.. blogs... etc.. get it out there... you need to entice people to you
Also, get some webspace wth some recordings of your show... so if people miss out they can find them and then see what you're like...