translate.google.com

Even though Esperanto isn't an option at translate.google.com, just for grins I entered an Esperanto word, with the source language set to "Detect language". The response was We are not yet able to translate from Esperanto into English.. It also detects Esperanto when words are plural, accusative, participles... Yeah, the detection code is probably independent and doesn't mean that the translation code knows anything about Esperanto (yet!), but the response sounds promising.