Great for those Mac users from Best of Gadgets.
15 Mac Tricks That Every Mac User Should Know
Shake up Learning has a nice article on google chrome extensions that can be used with your Google accounts (assuming you use the Chrome Browser.
Storyboard That is a great way for you and students to be able to create quick comics. You can do some very basic things without even signing up for an account. As with most things, you can upgrade your account for more features and images, but that is totally up to you.
Answer Garden is a great way to collect responses to any type of question you may have. From handheld devices to computers, you can collect responses from just about anywhere. You can embed the question with responses onto your webpage or simply use the responses as a way to build upon a lesson. There are lots of ways you can use it in your classroom, so visit their site to learn more.