The most popular is Kamenitza (could be spelt wrong!), but basically all the bulgarian largers are good. And at around 80p for 0.5 Litre bottle, even nicer!!
For a change try the dark Kamenitza which is smoother and not so gassy, not quite a bitter or a mild but still quite nice and worth a try. If you prefer Stella go to the Alps.
its zagorka all the way for me. Its lighter than kamenitza and not quite as gassy. You cant really go wrong with the lagers. Agree that the local beers are better and cheaper than the imports. Oh and the bulgarian red is very good.