MyFonts is a useful resource for all sorts of fonts, including a What the Font? tool that distinguishes a font from an image, or at least identifies the closest match:
http://www.myfonts.com
Check out this helpful grab bag of resources, such as GIF images in different sizes to use for mocking up page headers and menus, as well as a Lorem Ipsum generator for creating dummy copy to use as placeholder text:
http://www.designerstoolbox.com
Analyze your color choices for contrast with this nifty tool. Type in your text and background colors to see whether you provided enough contrast to comply with accessibility standards:
http://www.juicystudio.com/services/colourcontrast.php
Pick colors using this online color wheel, which gives you the hexadecimal number of every color along with the closest Web-safe color match:
http://www.febooti.com/products/iezoom/online-help/online-color-chart-picker.html
iStockphoto is an inexpensive source to find photos, background textures, design elements, and line art.
http://www.istockphoto.com
This free stock-photo site also contains tutorials, blogs, and articles about types of photo-related issues:
http://www.sxc.hu