Here is a nice summary of the Greek alphabet, its origins, its pronunciation, and its traces in modern European languages. It's interesting to see the first letters of the Greek alphabet as successors to older Semitic letters meaning ox, house, camel, and door: all the basic stuff right up front. Also, I never noticed before that omicron (ordinary o, as in "doll") and omega (o with a circumflex over it, as in "toad") came from o-micro (o-minor) and o-mega (o-major). Apparently "psilo" was another word for small, and formed part of epsilon (e-minor, short e, as opposed to eta or e with a circumflex, which was a long e or "ay" sound) and upsilon (u-minor, as in "duh," as opposed to double-u, too complicated to go into).
This site collects palindromes, more than I've ever seen in one place before. It got snagged, I guess, because of the idea of inverting strings of characters and still being able to read sense into them. Not interested? Yawn a more Roman way!
The search term "upside-down character" also led to this amusing discussion of linguists' struggles to transliterate the Greek "iota," also known variously as a jot, yot, or yod, sometimes rendered by adding an upside-down "breve" (little sideways parenthesis thing) to an "i":
So the 19th century philologists needed a symbol for [j]. When they were doing their work, the IPA wasn't around, so they couldn't have used that. In fact, even when the IPA was invented, historical linguists studiously ignored it anyway: they have never been interested in consistency with other subdisciplines, with the exasperating result that each proto-language has its own transcription conventions. (That's what we can blame the Uralic Phonetic Alphabet on.) Moreover, it would be unthinkable for philologists to explicate Greek forms using the Latin script: Greeks were the foundation of Western civilisation—so any historical linguistics to be done with Greek would keep the Greek script: any [j]'s would just have to be tacked on to it. (Of course, the same philologists didn't have compunctions about transliterating Sanskrit; it was not European, after all. Not sure what the excuse was for transliterating Old Church Slavonic, but I'm sure they could come up with something.) To this day, IPA is unknown territory for Ancient Greek historical linguistics.
So if you wanted a character for [j], you searched close to home. As Haralambous documents [§1.2.2], if you were working in the German tradition, you used j, which happens to be the German grapheme for [j] (and which also ended up the IPA's choice, much to the chagrin of Americanists). If you were working in the French tradition, you used y, because it wasn't German. Haralambous observes that more recently French scholars have switched to j, because it's in the IPA; given the year I'm writing this in, I suspect it has the added advantage for the French that even if it is German, at least it isn't American.Finally, this site lets you type upside-down, a useful bookmark if ever there was one. But I still don't know how to transliterate my upside-down Greek M's.
Not sure if you'll be able to see this small attachment, but try Eric's right-click trick. The character appears where we'd apparently expect an ordinary M; the Greek gurus at Project Gutenberg are drawing a blank on why they'd have been inverted.
SEPTI[M]ION OUORODÊN TON KRATISTON
EPITROPON SEBASTOU DOUKÊNARION
KAI AR ... APÊTÊN IOULIOS AURÊLIOS SAN[M]ÊS
[M]ASSIANOU TOU [M] ... LENAIOU HIPPEUS
RHOU[M]AÔN TON PHILON KAI PROSTATÊN
ETOUS Ê O PH[**numerals; date] MÊNEIXANDIKÔ.
The image cut off the last line, but it's not important. The ellipses correspond to areas where the original inscription was worn away and illegible.