I have a kitchen and a bathroom sink both seem to be draining very slowly. The Kitchen sink was initially not draining at all, so I cleaned out the vent and got an amazing amount of crap out of the clean out. I snaked away from the house, but the snake came back clean.
I should also add that I have occasionally had things that I flushed down the toilet come back up. Any input would be greatly appreciated.

City sewer or septic? You named 2 sinks and a toilet, what other fixtures are in this home and how do they drain?