If you are playtesting early builds, it's good to test in-person. You can actually observe players getting frustrated, discovering exploits, or having fun in real-time, and it's easier to ask them questions immediately after they are done testing. For indie games, simpler solutions are often better.
Put your game on a laptop and go to a place where people are hanging out. If it's summer, head for an ice-cream shop and ask people to play your game. Coffeeshops are great for this too. Check out the location beforehand and verify that there are power outlets and that you can have a conversation without yelling, though.
You can put up paper posters at local colleges and schools. I strongly recommend reaching out to middle-schoolers, as they have the skills to play pretty complex games with none of the shyness. (They will tell you exactly why a game sucks to your face.) Science/technology/math teachers may let you test a game with their students in exchange for a talk about game development or programming.
Once you're starting to test for stability, definitely put together a friends-and-family email list and send them builds. People who know you will be more likely to get back to you quickly, especially if you need esoteric details from them, such as their processor and graphic specs.
Of course, you want to be able to reach out to total strangers as well, but don't ignore low-hanging fruit.