Dunno if a comperhensive list exists but I'm bored at work so I recommend all of these:
Black Cat Cafe, Hackney Central: All vegan, burgers, curries, salads etc.
Fed by Water, Dalston: All vegan, pizzas and other Italian stuff.
Voodoo Rays, Dalston/Shoreditch: Giant pizza by the slice or the whole 22" shebang, v.good.
The Gallery Cafe, Bethnal Green: Lots of options, they do theme nights too so check the website.
Cook Daily, Shoreditch Box Park: Veggie salad bowls with a cult following.
Vegan Doner Kebap , Pump street food in the old petrol station Shoreditch: Vegan kebab!