Symbaloo is a great tool for gathering website links in one place to share with students. It is basically visual bookmarking. You can link to websites, online documents (like Google Docs), videos, and more. You can see Symbaloo at work on the 'Teachers' page of this site, along with every grade level page. The links are created in a grid-like box that is called a webmix.
Symbaloo has a free EDU version for teachers, and also a Pro version that has more features. You can use other people's webmixes and/or create your own. The webmixes you create are very easy to edit and share. The tiles (which are the links) that you create can also be color-coded to help with organization. And you can share your webmixes publicly or make them private.
Check out this introductory video to learn more about how Symbaloo works.