Bitly is one URL shortener that I have been using for years. It's simple to use, especially if you use the bookmarklet, allows you to customize URLs, and it offers good statistics about the use of your links. Bitly offers an option for bundling bookmarks into one package that you can share with just one link. Bitly bundles can be created collaboratively if you invite other Bitly users to bundle links with you. The nice thing about Bitly is that you can view how many times a link has been used. So if you have 25 students and the link has only been used 20 times, you know that at five students aren't where you need them to be.
LinkBunch is a free service that you can use to quickly send a group of links to your friends, colleagues, and students. To use the service just visit LinkBunch, enter the links that you want to share, and click "Bunch." When you click on "Bunch" you will be given a URL to share with anyone you want to see the links in your bunch. When someone clicks on the URL for your Bunch he or she will be able to open the links you bunched together.