Standards formats for this are 88x31 and 80x15. See Web badges (wikipedia)Â for more info and zwahlendesign for many examples.
Brian Kent has plenty of nice microfonts that you are apparently free to reuse in any context. Microfonts in this collection: Acknowledge TT, Alpha Beta, Homespun TT, Lights Out, Mini Kaliber S TT, Nanosecond Wide, Nanosecond Thick, Nanosecond Thin, Ryuker, Setback TT, Visitor TT1, Visitor TT2, Yoshi's Story game text, Zelda DX TT, ∆ Systematic TT
Let's give it a try:


(an image is supposed to appear, but it sometimes takes a bit of time to load, despite the small size)
Feel free to reuse. Simply put your mouse over one of the images and right click to get to the menu that lets you save the image.