http://www.ibiblio.org/koine/greek/lessons/alphabet.html had a web
page that lists greek pronunciation. I wanted to make a Unicode
version. The unicode will not be as portable as the inline image that
they include on their page, I admit.
This table gives the Greek letters, their names, equivalent English
letters, and tips for pronouncing those letters which are pronounced
differently from the equivalent English letters.
Sigma (σ, ς):There are two forms for the letter Sigma. When written at the end of a word, it is written like this: ς. If it occurs anywhere else, it is written like this: σ.
Upsilon (υ):In the above table, we suggest that you pronounce this letter like "u" in "put". The preferred pronunciation is actually more like the German "ü" as in "Brücke", or like the French "u" as in "tu". If you do not speak German or French, don't worry about it, just pronounce it the way the table suggests.
Xi (χ): This is the same sound as "ch" in "Bach", which does not sound like "ch" in "chair". The same sound occurs in the Scottish "Loch", as in "Loch Lomond", or the German "ach!".
To be fair, we should mention that there are several different ways to pronounce Greek. We are teaching the Erasmian pronunciation for now. At some point in the future, we may add pages to teach some of the other pronunciations. Here are the main ways that Greek is pronounced: