I purchase all my commercial fonts from Fonts.com - I LOVE that place! I signed up for their newsletter and just get giddy when I get an email. I am a bit of a font freak (wannabe) lol.

As for standard web-fonts, I use Arial, Georgia, and Century Gothic which each cover standard fonts and can be manipulated for cool effects. For instance Arial in all-caps is pretty cool and then Georgia in italics is like its own other font. With CSS you can manipulate all kinds of things with the fonts - even the spacing between the letters. I love it!

Otherwise, all fonts for commercial purposes must be purchased and licensed just like all our stuff does. Kind of a bummer, but I find that you can get just top-quality fonts that way so to me it isn't a big deal.

Oh, and one place you can get some fonts to play with is fontgarden.com That is definitely my favorite font site and if I remember correctly they have some really good prices for commercial use :)