7 Cups of Tea
I'm actually a listener on this site to help those in need, and I think this is one of the best sites out there. You can easily create a member account (or chat as a guest) and be able to connect to a listener and have an online chat with them about whatever you're struggling with. Even if you're just feeling lonely, there will be someone online at all times to talk to you. None of the listeners are paid, they do this for free and most of them are very professional and compassionate. The listeners are not allowed to provide advice because no one knows what's best for you because they are not you, but listeners can obviously listen and provide helpful suggestions and encouragement.
This is a community/subreddit on Reddit.com where people can.... well, get things off their chest. It's right there in the title! All you need to do is sign up for a Reddit account and then click on the 'get something off your chest button' and you'll be able to make a post. People will then be able to comment on your post and give you advice or words of encouragement, or you can go write a comment on someone else's post. It's very convenient and much easier than both 7Cups and BlahTherapy because with this you just have to sign up and post one comment to get everything off your chest, while with the other sites you have to not only register but you have to connect with a listener and have a chat session with them. Do be warned that sometimes people can be rude and unhelpful on this subreddit, but the vast majority of people on r/offmychest are kind. There's also subreddits like r/randomactsofkindness and r/assistance if what you're struggling with is due to financial issues.