Wiktionary
A publicly edited international dictionary providing words and phrases’ etymologies, translations, inflections, and meanings. I have never found it to be inaccurate.

Phrontistery
A compendium of obscure words.

По-русски
For beginners in Russian. Contains a large number of short stories.

OpenRussian
A collection of some of the most common words in Russian, marked with stress.

Poetry Reader for Russian Learners
Poems of famous Russian authors with translated vocabulary and stress-marked words. An immensely useful website for those aspiring to read Russian literature in Russian.

Latinium
Latin articles, audiobooks, and discussions of grammar and Roman history.

Latin Core List
A list of the most common words used in Latin.

Cupiditates de Elysii
Pirated L.L.P.S.I.

Vicipaedia
Publicly edited Latin articles. Their quality varies, but at least there’s a lot of vocabulary that can be learned.

Neo-Latin Lexicon
What it says on the tin. The downside is that it’s pretty laggy.

List of Latin translations into modern literature
Latin reading material not made in ancient times.