Writing Resources -> Writing Prompts
On the left side of your screen, you will see a link to Writing Resources. One of the several things listed is Writing Prompts. You can either add your own writing prompts into the already large list, or you can refresh the page and get some new writing prompts, continuing that until you find one that interests you. WdC also puts out an iPhone and Android app for writing prompts, and those can be used "on the go", so to speak. They just might have the new idea perfect for jump-starting your flow of thinking again.

Read Other People's Stories
While it seems odd, sometimes an author can glean ideas (their OWN ideas, hopefully) while reading the stories of others. Specific nuances of a story or character can trigger a reaction in your own brain that just allows you to take off running. Luckily, Writing.Com has a very large amount of stories to choose from in this manner.

Review Other People's Stories
When all other kinds of writing fail, try offering a review to someone. It gets your mind working and your fingers typing, even if it isn't the creative sort of writing you may have been looking for. It's a start, and it can certainly lead to awesome solutions! You get the benefit of feeling good about helping another author, and you get something down on a page. That story may come later, it may take a bit more effort, but the important part is to GET WRITING... by whatever means necessary.

Keep A Blog
Blogging has become more and more popular amongst all generations, and all walks of life. You can pretty much find a blog about anything you'd like on the internet - food, gadgets, relationships, or just someone documenting their own daily events - whether interesting or not. It is another form of journaling, albeit a much more public one, and it also gets the fingers moving toward getting some ideas out on a page. Not to mention... blogging is awesome because sometimes frustrations can be let out in that manner. A mind clear of frustrations sometimes finds it easier to write.