How can you write in a langauge so everyone can read it without needing a special font (character set)? Write in Unicode, a standard designed to include all languages. Not all software is compatible with Unicode and there are other issues as well, but here are some fonts available with Windows or free on the Internet.
Although the standard font in Microsoft Word, Times New Roman, has a large range of IPA symbols, it does not include many characters in the Unicode set. (The standard font Calibri in Office 2007 seems to have the same range as TNR.) Arial Unicode MS and Lucinda Sans Unicode come with recent Windows and Office editions. See Description of the Arial Unicode for instructions on installing Arial Unicode MS. Sacred-texts also recommends the Code2000 font; I haven’t tried it yet, though Norton tells me it is virus-free.
Another option for a wide range of symbols is Chinese-based fonts. Although the Chinese font Simhei, for example, does not have a wide selection, Gulimche is a good Korean font with a wide, though not comprehensive set. 明朝 is a Japanese font with a similar set of characters. To access these fonts, you generally have to go to the language settings in the control panel and add those languages, then go to Start -> Programs -> Microsoft Office -> Microsoft Office Tools and make the appropriate setting with the language tool.
Also see the SIL font posting for three more free Unicode fonts.