Some sites for acquiring typefaces:
Browse by category or name. Rating system allows you to see which are the most and least popular. If there's a specific typeface you want, you can use their site search (which suggests similar search terms as well). Character map preview available before download. Appears to only have TrueType format available.
Has a pop-up for fonts.com when you visit. Includes instructions for installing fonts. There are even instructions for converting from Windows to Mac versions of files (see their Mac help page for details). Browse by category or name. Downloads are in zip format. There are links to other sites where you can find font files as well. Preview typeface name only before downloading.
Blambot Comic Fonts and Lettering
This site caters more to those looking to create comics, but has a a good variety of hand-rendered and display typefaces. Organized by category, then by name. Coloured dots indicate typefaces you have to pay for to acquire and limited availability. Typefaces without a dot are free. Various file formats available. Indicates variations included with the typeface (regular, italic, etc.) before downloading.
Comics and Cartoon Lettering Fonts
A list of various sites where you can find font files for comics dialogue, compiled by Hans Presto. Also worth checking out if you need hand-rendered typefaces.
A popular source for font downloads. Includes installation instructions (Windows and Mac). Organized by category, alphabetically, and by author. You can even create an account to submit fonts you've created. Download in zip format. Character map preview available before downloading.
Browse alphabetically by name. Downloads available in zip format. Requires typing in a verification code before you can download. Preview of font name only.
Browse alphabetically. Character map preview available before downloading (click on typeface name). Various file formats available.
Free in TrueType format, even for commercial use. Read help for details about restrictions. OpenType and PostScript variations available for a fee. All downloads via MyFonts.com, with character map preview available.
You can find free fonts with the site search, but there are primarily pay fonts here. You can also use one of their various options for finding or identifying fonts to browse.
When you can't remember the name of that font you're looking for, this site can help you identify it visually. Just choose the options that apply and and it will generate results for you. Character map preview available before you buy. Downloads are pay only, via FontShop.com
And an article you may find interesting:
The Scourge of Arial
A brief history of Helvetica and its imitator, Arial. Check out the "How to Spot Arial" article as well.