The Library of Congress Chinese Romanization Guidelines
Catch-all but slow to download with many graphic files.

Romanization Conversion Table
Java applet that converts some of the more common Romanization systems for Chinese.

Pinyin to Zhuyin to Wade-Giles
Conversion table in Chinese.

Wade-Giles to Zhuyin to Pinyin Conversion Table
Based on the "Correspondence of Wade-Giles to Pinyin" list included in the Library of Congress Chinese Romanization Guidelines. (Requires a Chinese text supporting browser).

Pinyin to Wade-Giles Conversion Table
Does not include syllables which carry the same romanizations, e.g., fan, lin, min, etc.

Wade-Giles to Pinyin
In Chinese.

HML Pinyin
Romanization without the diacritic marks by Tham Wai Houng.