What are some positive and negative things interest groups have done for the country?
This is entirely a matter of personal opinion. Interest groups represent the interests of a certain segment of the population. If an interest group accomplishes something that you don't like, you'll call it negative, but someone else might think it's a positive.
For example, the National Rifle Association (NRA) has succeded in getting many gun control laws repealed. This is something that people who believe in gun rights would think is a positive. However, liberals would tend to think it is a negative.
Interest groups make the opinions of the people heard. Because not all the people have the same opinions, some will think that the actions of a particular interest group are good while others will think they are bad.