Because I fulfill some work for Ukrainization of my computers (since 1992), I wish to place all its parts together. Look also at my projects page for several packages for miscellaneous programs Ukrainization.

So, there are several charset for Ukrainian, most important of them is listed below.

RUSCII, as defined in the RST 2018-91. Also known as CP1125.
It's a standard Ukrainian charset for DOS and OS/2. You may download my package for DOS Ukrainization (dos4ua.zip, 14 kb) or screen fonts (4 kb) for this charset (8x8, 8x14, 8x16 dots). Because Win32 console also use DOS encoding, you may download CP1125 screen fonts for windowed console mode apps (vgaoem.fon, 8514.fon, dosapp.fon; 18 kb).

KOI8-U, as defined in the RFC 2319. It's a most popular standard for *NIX and default transport encoding for Internet mail and news.

CP1251, as defined by MicroSoft, Inc. It's a standard Cyrillic charset for MS Windows family, which covers Byelorussian, Russian and Ukrainian characters. You may download my package with keyboard layouts for MS Windows 3.1* (win4ua.zip, 14 kb) and for MS Windows 95 (w954ua.zip, 3 kb). On my projects page you may find packages for Ukrainian support in some Win* programs.

MAC Ukrainian, as defined by Apple, Inc. Unfortunately, I don't have an Apple computer, so can't say anymore about it.

You may also look at the other cyrillic charsets:

• CP866, standard DOS codetable in Russia. Include Byelorusian 'short U' and Ukrainian 'IE', 'YI'; but no have Byelorussian-Ukrainan 'I' and Ukrainian 'GHE with upturn'. So, this charset is unsuitable for serious work with Ukrainain.
• KOI8-R, standard *NIX codetable in Russia. See more about this charset at the Ache's homepage.
• KOI8-RU, MicroSoft's variation of the KOI family, including Byelorussian 'short U'.
• ISO 8859-5 (aka GOST 19768-74), old Soviet Union standard, now used in Sun workstations.
• KOI-7, one of the first Cyrillic charset, use only 7 bits, so have no Latin characters. It have variation with no lowercase cyrillic, but uppercase latin in the 0x40-0x5f position. Some terminals allow to switch this charsets.
• ASCII, American Standard Code for Information Interghange, 7 bits only. All of the above Cyrillic charsets (except of KOI-7) use it for lower-half of character table.

I'd use some info from Fingertip Software Cyrillic Character Sets page and Roman Czyborra The Cyrillic Charset Soup page.