When CTAN was young, most people would start using TeX with a 300 dots-per-inch (dpi) laser printer, and sets of Computer Modern bitmap fonts for this resolution are available on CTAN. (There are separate sets for write-black and write-white printers, as well as sets at 120 dpi and 240 dpi.)
There used to regular requests that CTAN should hold a wider range of resolutions, but they were resisted for two reasons:
If your output is to a PostScript-capable device, or if your output is destined to be converted to PDF, you should switch to using Type 1 versions of the CM fonts. Two free sets are available; the older (bakoma) is somewhat less well produced than the bluesky fonts, which were originally professionally produced and sold, but were then released for general public use by their originators Y&Y and Bluesky Research, in association with the AMS and other scientific publishers (they are nowadays available under the SIL’s Open Fonts Licence). The two sets contain slightly different ranges of fonts, but you are advised to use the bluesky set except when bakoma is for some reason absolutely unavoidable. In recent years, several other ‘MetaFont’ fonts have been converted to Type 1 format; it’s uncommon ever to need to generate bitmap fonts for any purpose other than previewing — see “previewing documents with Type 1 fonts” — if even then.
More modern fonts may be used in place of the Computer Modern set. The EC fonts and the Latin Modern fonts are both close relatives with wider ranges of glyphs to offer.
This answer last edited: 2011-09-4