Mid-priced lounge/nightclub downtown
For a place that's fairly large and has both food and coctails, try the Chocolate Bar on King E (across from George Brown College). It's fairly new, the owner is very nice and the staff are super. There is a DJ and they have a back room that's more lounge than restuarant. Their sweet martinis are delicious.
If you want to venture to the west-end, where I think everyone should be :), go to the Chelsea Room on Dundas W (I forget the intersection). It's a very low-key interestingly designed space, every night there is a different musical spin (Tuesdays are fun, because local DJs or wanna-be's take over the turntables). They have no real food, however, only frozen dinners to cover the liquor license. Their mixed drinks are good.