Living Poets is a Durham University website with short guides to various ancient Greek and Latin authors, such as Homer, Orpheus, Anacreon, Catullus, Ovid, and Virgil. The guides focus on the extant sources and how the authors were received in their lifetime and by later generations, avoiding the "perils of autobiography."
Humanities and the Liberal Arts is the personal website of former Middlebury classics professor William Harris who passed away in 2009. In his retirement he crafted a wonderful site full of essays, music, sculpture, poetry and his thoughts on anything from education to technology. But the heart of the website for me is, unsurprisingly, his essays on ancient Latin and Greek literature some of whom are book-length works. Here are a few examples: Purple color in Homer, complete fragments of Heraclitus, how to read Homer and Vergil, a discussion of a recently unearthed poem by Sappho, Plato and mathematics, Propertius' war poems, and finally, especially close to my heart, his commentaries on the poetry of Catullus, for example on Ipsithilla, Odi et amo, Attis poem as dramatic dance performance and a couple of very dirty poems (even by Catullus' standard). That's just a taste of the riches found on Harris' site, which has been around nearly as long as the world wide web has existed.
Brindin Press has lots of poetry translations into English online, concentrating on French, German, Italian and Spanish, though more than 40 other languages are represented as well. A boatload of translators is represented, from those toiling in obscurity to big literary names (e.g. there are translations of Catullus poems by Ben Jonson, Jonathan Swift, Louis Zukofsky, Aubrey Beardsley and Thomas Hardy). There is also a section of quirky poems. Finally, here's a rendition of Goethe's Der Erlkönig that substitutes the elfish king with a dalek.
ArtMagick is a collection of art and poetry that roughly dates from after the Enlightenment but before Modernism. While the poetry section is extensive the main draw is the sites extensive art collection, which can be browsed by artist, art movement, title, theme or albums created by the site's users. So, forget the summer heat with some chilly pictures of winter, check out famous objects of devotion or search the archive.
Can't hack Catullus in Latin? How about Brazilian Portuguese, Catalan, Chinese, Danish, Dutch, English, Estonian, French, German, Hungarian, Irish, Italian, Japanese, Norwegian, Polish, Portuguese, Rioplatense, Romanian, Russian, Scanned, Serbian, South African, Spanish, Swedish, or Welsh? You can also compare two languages side by side.