Nothing evil about giving a healing potion to a strung out junkie, then shutting down a ring of drug dealers. Likewise with finding Mjoll's sword, giving money to a beggar, finding jewels for Madesi and Talen-Jei, finding an old journal for Brand-Shei, gathering ice-wraith teeth for one of the other merchants... I'm sure there's other non-evil stuff, too.
The Thieves' guild stuff does tend to dominate things though.
Many of these are not TG quests, though, which is more what OP is asking about.
Once you join the guild and have to start shaking people down and threatening/blackmailing shopkeepers, people will start reacting differently to you in town.
I'm playing a good guy for the most part and finding the comments of townsfolk in riften particularly poignant, especially for a good character- they're looking for a reason to hope and trust. And there's Mjoll, who's sort of the town's protector, and all of the obvious corruption with the Black Briars- it looks like there really would be some kind of way to "help" this town for good rpers, but it doesn't look like it. Once you join the guild your job is to make them feel hopeless. Sure they say they distinguish themselves from the DB because they don't kill but they have no problem with ruining peoples' lives.
I was hoping there might be a way to take down the guild from the inside by doing the quests but have put this questline down because you have to get your hands pretty dirty to do it and that's not the type of character I'm playing. Maybe for my usual evil female second character, though.
You
can put a dent in the Skooma trade, though, and help a bunch of random people.