Kaseriani Monastery and Gardens, Kaseriani Monastery (It's easiest to take a taxi.), ☎ +30 210 723 6619. A nice escape from the city in the foothills of Imitos. Walking trails. There's a functional monastery one can walk in, and several ruined chapels or basilicas up on the walks.
Laiki (People's market), Divaki Pindou and Ioanni Theologou. A fruit, vegetable and fish market. Good fun.
Ta Duo Adelfia (Ταδύοαδέλφια), Papagou. The best souvlaki in this part of Athens. A guro will cost around €2.
Thanasis, Grigori Kousidi. Good souvlaki, try there "pitta kalamaki kotopoulo me sauce" (Chicken kebab wrapped in a pitta with sauce), because it tastes fantastic!A guro will cost about €2.20.
There are a whole bunch of standard cafes here which cater the hordes of students that study here, and the large numbers of old men who sit around all day drinking ελληνικούς (Greek coffees). But there are a few gems worth trying out if you want something different.
Playce, Str. Papagou 128, . A really nice cafe where you can play board games whilst drinking your coffee. Has a very anime feel to it. Very popular.