Some Quick Info on Licensing and Copyright Use
Keep an eye on licensing and use. Many things are free for personal use, but not commercial use. For example, a teacher looking for a graphic for her math worksheet she made. Some things have a commercial use but with limitations that it cannot be used for printing services like t-shirts or greeting cards.
Fonts used as a typeface has no copyright. If you write a book, you can use any font you want without infringing upon someone's intellectual property. But fonts used in design, like a facebook meme or t-shirt, those have some copyright to them, especially the computer code. It was said a loophole around it is to print up the font, scan it in, and make your own from that (to circumvent using someone else's computer code of anchor points and what not), but if you want to be safe, in your designs, use fonts you know you are allowed to use. Some of the ones in the program's package, like Photoshop or MS Word, are only free to use for personal use and not commercial use. The best thing to do is google the name of the font, and make a judgment call based on that.
Public Domain means you can use it for any reason. While each country has their own copyright laws, in the US, anything from before 1923 is GENERALLY considered public domain, but that doesn't mean it's true. It's just close enough for most people to attempt. Anything made by the government is considered public domain, for most situations, but again, some exceptions to the rule exists (for instance, the government trademarks certain things like the Air Force Logo).
The best free fonts are made by Ray Larabie. He has some for free, and some for sale. You can fish through his long list of fonts searching for the free ones (which are perfectly good, professional fonts), or you can pay 20 bucks for an ultimate download. I use his fonts the most of all free fonts I ever downloaded. He has the largest list of free fonts of any designer I have found on the web, and I frequently spot his fonts on commercial advertising and t-shirt designs. It's weird, walking through Walmart, seeing a t-shirt, and going, "That's Ray Larabie's Budmo Jiggler."
Blue Vinyl fonts has some for free, and some for sale. The free ones include both lettering and dings, and her dings are genius for the designer. I frequently use 60's chic for the little retro sparkle star.
Vic Fieger has a lot of fonts on Dafont and more professional versions on Cheap Fonts Pro.
Dafont is a site of free fonts, but you will have to search for the license. Some fonts have a "read me" file with them that stipulate license use, so you sometimes don't know how you can use it until you download it and extract it (right click, extract files).
Wikimedia Commons has probably the most extensive list of free pictures and photos you can use. Each graphic usually tells you the license (i.e. Creative Commons) or if it's in public domain. Creative Commons has some weird stipulations that make you question some commercial use; however, keep in mind, when you upload a picture to Wikimedia, they only let you choose between standard licenses. There is no "put it in public domain" option. Use your best judgment.
Nasa has some amazing photos you can use because it's government and public domain.
The military websites have photos you can use, again because it's government and public domain. Air Force. Army. Marines. Navy. Just don't use their trademarked stuff like logos and seals.
Pixabay has a public domain listing of images people have placed in public domain. Beware, some of them might lie about it.
Wikipedia's huge extensive list of where to find images in public domain.
Every Stock Photo has a lot of pictures free to use, but read the licensing info close because they aren't all that way.
Morgue File has a lot of pictures free to use, just stipulated that you can't use it in a stand alone manner.
Flickr Commons has many public domainy resources submitting to their library. You'll have to look for licensing information, but it seems most are free to use for any reason.
Bing's Images lets you filter search results by license type.
Clickr has a bunch of clip art graphics in public domain.
Flaticon has a bunch of free vector graphics and a font face generator.
Free Photoshop Stuff
Brusheezy has some of the best quality textures, brushes, patterns and shapes. The license information is included with each piece.
Obsidian Dawn has a lot to offer the world of Photoshop, but she has some stipulations. For commercial use, you must link back or give credit; however, you can purchase a commercial license to not have to do that.
Arbent offers free brushes for personal and commercial use.
My Photoshop Brushes has some free for commercial use, but most offered are free for personal use only. The license is stipulated with each graphic element.
Of course, the best way to find what you are looking for is to use a search engine, and search the specific brush or pattern you want, for instance, "Photoshop Brushes Ice," and then research the options for licensing purposes. This is pretty much the only way I do it anymore.