In French, the acute accent is used only on the letter e, where it changes the vowel sound: é [e], and e [@].
In Swedish, the acute accent is also used only on the letter e, mostly in words of French origin and in some names, and mostly (only?) on the last syllable of a word. It is used both to indicate a change in vowel sound, same as in French (and Hungarian and Icelandic), and that the stress should be on this, normally unstressed, syllable. Examples include resumé (accent on the last e only!) and Linné (which is the way the name of Carolus Linnaeus is normally spelt in Swedish).
In Spanish, Portuguese, Catalan, and Greek, the acute accent is used to mark the stressed vowel of a written word that would normally be stressed on another syllable. Stress is contrastive in those languages. E.g., in Spanish ánimo ['a-ni-mo] ("cheer up!"), animo [a-'ni-mo] ("I am cheering"), and animó [a-ni-'mo] ("he cheered") are three different words.
In Spanish and Dutch, the acute accent is used to disambiguate certain words which would otherwise be homographs. In Spanish, various question word / relative pronoun pairs cómo & como (how), dónde & donde (where); in Dutch, mainly één (a/an) & een (one), and vóór (before) & voor (for).
In Dutch, the acute accent can also be used to emphasize an individual word within a sentence.
In Hungarian or Icelandic, the acute accent is used to mark the quantity or length of the base vowel. This is the same contrast that differentiated long and short vowels in classical Latin, or that nowadays diferentiate simple and double vowels in written Finnish.
In Polish, the acute accent is used over several letters, both vowels and consonants. Over consonants, it is used to indicate palatization much as the háček is used in Czech and other Slavic languages; eg. sześć [sheshch] (six).
In Czech and Slovak, the acute accent is used to indicate a long vowel. A "long vowel" in Czech means a vowel that is sustained for a greater length of time; it does not have the same meaning as a "long vowel" in English. The letter u can have an acute accent only at the beginning of a word in Czech. To indicate a long u in the middle or at the end of a word, a krouek (ring) is used instead, to form ů.
In Vietnamese and some other tonal languages, the acute accent is used to indicate a rising tone.
A number of English words are written with the accute accent, mainly those borrowed from French. Such words include résumé, fiancé and fiancée, sauté, and roué. The accent is commonly only retained where the word as spelled would tend to be pronounced differently if the accent were not there.
Using the ISO-8859-1 character encoding, one can type the letters á, é, í, ó, ú, and ý. Dozens more letters with the acute accent are available in Unicode. Unicode also provides the acute accent as a combining character.