Singer's Babel * offers tools to help you learn the meaning and pronunciation of texts found in art songs, song cycles, oratorios, cantatas, and secular and sacred choral music. Hear a native speaker reciting the text while you read the original text. Also includes word-for-word and IPA translations.
Naxos Music Library * is generally for listening to music, BUT many of the albums have the original liner notes that have translations! To find them, look for an album that has your song, open it, look on the left side of the screen for the link to the "booklet." Open it and generally there will be translations!
LiederNet is a great, FREE resource for translations of many art songs. While many are great, remember that they are not all vetted through a scholarly process, so the quality can sometimes be hit or miss.
The library collection has many different books with song and aria translations. The majority of them will have call numbers that start with ML48 or ML49 (for opera and oratorio libretti) and ML54 (for art songs of all types). Some examples of some of the great books include the following:
Frequently, many newer song anthologies will also have translations (IPA, poetic, and/or literal).
Finally, to find other books that may have this information, try the following search strategies: