LOok into the Glyph panel.
If you're using Windows, there is an incredibly useful utility Babelmap that has the tool you need: "List all the fonts installed on my system that support the text I have on my clipboard". I used to use it all the time.
I very much doubt that you have many fonts already installed on your system that support Old Slavic, unless you've installed them yourself. Bulgarian coverage is better, but still not common. If you'd like I can post some links to the pages where links to the type foundries working in these scripts are often posted. If you're not already familiar with it, Paratype is probably going to be your first stop.
Thank you! I'm started to use InDesign, very interesting adenture. There is no good cirillic in Adobe Garamond Pro (and I have to set book about slavic linguistic... ) but I helped myself. Thanks for Babelmap, Joel, I'll try it!
cheers from Toruń in Poland,
I'm pretty sure that you received Garamond Premier Pro along with CS4. Some weights of it, at least. It has Cyrillic support, at least for plain-vanilla Russian. I don't know about Bulgarian, though. You may want to look at the powers of a tool like IndyFont because it is sometimes hard to find a really good font that has all of the extended-Latin and extended-Cyrillic one needs for multilingual work.
If you really want a fully featured OpenType font that has a very wide
support for Cyrillic, Slavic, Lithuanian and more (IIRC), take a look at
Agmena Pro, a beautiful new typeface by Jovica Veljovic. I've used it in
a couple of books now, and the results are great.