Small corner sofas look a lot like Corner Group Sofas, but generally smaller. More ideal for apartments and small areas of your house. They can come in all the same colors and fabrics as the larger ones, even the same styles.
Small corner sofas generally have space for 2, maybe 3 people where as the Corner group sofa would have room for 5 or 6. Some people would ask why would you get a corner sofa if you are looking for a sofa for a small area. Sometimes small corner sofas are the best fit. Other small couches might not fit properly into a corner and therefor you can use more of your open area for other things. There is a scale that some people go by when wanting to know if a small corner sofa is good for them. 
Lets say the measurements for a small couch and 2 chairs,
Adding those numbers together would go as follows,
- 72" + 24" + 24" = 120" wide
Now you have an idea of how big the small corner sofa could be, some people add a little more to that just to make sure that the sofa is big enough for your needs, but not to big where it will be too big for the room.
Another good idea would be to measure the space that you need to fill. When doing so take note if you want any floor lamps in that area or anything else. With those measurement you can go to the local furniture store and see what styles they have. When looking remember that if there is a style you want but it's the wrong color a lot of the times they can order you a sofa in a different color. That way the new couch you get can blend in with the stuff that you already have in your home.
Good luck with your small corner sofa search, if you have any questions or comments please contact use. We would appreciate any feedback you can give us.
Likewise I would like links. I need a corner sofa which is 72 x 72. Any ideas. On a budget as well and would even consider second hand? travelbug1981@yahoo.co.uk