Here's a big list. Keep in mind that there area good/bad pockets virtually everywhere in Toronto, and within a few blocks of a lot of so called "ghetto's" and lower income area's, you can almost always find big, expensive houses, or quiet suburban streets at the least.
- Rexdale and North York/West side of the city: Finch and Albion, Bergamot, Jamestown, Stovetop, Mount Olive, Orpington, Tandridge, John Garland and Martingrove, Finch and Weston, Lawrence and Weston, Islington and Weston, Eglinton and Weston, Scarlett and Lawrence, Scarlett and Eglinton, Scarlett and Thretheway, Kipling and Steeles, Martin Grove and Eglinton, Willowridge, Martingrove and Rathburn, Rathburn and The East mall, Burnhamthorpe and The West Mall. (I've been robbed at gunpoint at Capri Rd and The East Mall at night, in front of some public housing highrises) Golfdown Drive/Armel Court / Thistletown. Places near The Westway area just south of Rexdale.
- Pretty much the whole Jane strip from Bloor north to Steeles, and many offshooting side streets. Also, a lot of side streets along Weston Road and Sheppard Ave West.
- Scarborough: Chester Le, Cataraqui, Galloway, Cougar Ct., Danzig aka D-Block, Dean Park, Dolly Varden, Galloway, Gilder, Glamorgan, Glendower, Gordonridge, Greenbrae Ct., Malvern, Markham and Eglinton, Markham and Lawrence, Mornelle Court, Orton Park, The Pentagon, Silver Springs, Teesdale, Tuxedo Court, White Blocks, Bay Mills, Areas around Don Mills and Finch, Finch and Victoria Park, Midland and Mcnicholl, Midland and Finch, and many more. Again, there are a lot of bad hoods in Scarborough, and a lot of nice ones too.
-Don Mills and Eglinton (Flemingdon Park aka Flemo) and some surrounding areas, Mt Dennis and Don Mills, Overlea.
- Areas along Keele street can get a bit scuzzy, although nothing really bad until you get to Sheppard and further North.
- Lawrence Heights aka Jungle and Neptune (Near Lawrence and Bathurst/ Allen Road) and a few streets Near Ranee Ave.
- Pellam Park (St Clair West and Weston Road)
- Vaughan Rd and Oakwood Ave to Eglinton West and Dufferin.
And then of course there are the downtown hoods.
St Jamestown, Regent Park, Moss Park, certain spots of Cabbagetown/Parkdale (esp. King and Dufferin). Rivertowne/Don Mount Court used to be pretty ghetto/isolated, in between Regent and the Don River, but I believe most of it was demolished and left as empty land.
Edit:Forgot to mention Lansdowne from Bloor to Queen. Lots of crack and prostitution around there, though it used to be worse in the late 80's/early to mid 90's
In my experiences, I see more junkies, bums and crazies downtown (higher density) but usually feel safer there for that exact same reason, even at night... There are many areas in Toronto that are completely isolated/abandoned after dark that are known for high crime and drug/gang/prostitution activity. The last area like that I was near was Weston Road and Lawrence West.