For several years now, I've been happily using
Surfulater. At $79, it's a bit pricey, but that price permits you to use it on up to five computers. I'm happy that I was able to get it for less, but knowing how well it serves my needs, I'd willingly pay the full price if I had to. What do I like about it? Well, I can save material from just about any source, online or off. Most of the time, I simply right-click on an article, or part of an article, or a website that I want to save and select one of four possibilities: Add new article, Add new article plus Page, Attach Page to Article, or Bookmark this Page. To be honest, I almost always select the first option: Add new article. Surfulater automatically records the source of the article, and I can easily edit the article, link it to other articles, add tags to make it even easier to find, etc. I can also search my database(s) VERY quickly. And if I encounter a problem, there's a forum and a very responsive developer to turn to for help.
All in all, I'm very happy with Surfulater. Admittedly, I'm a little nervous about the developer's plans to have the next version make use of the cloud, but apparently one will still be able to have one's database on one's computer (my preference, at the moment). However, at least for now, I recommend Surfulater very highly as an information manager.