A place we have really been enjoying lately is Vasaros Terasa. http://www.vasarosterasa.lt/ This is a nice little secret that you may not have discovered, because although it is on Vilniaus it is kind of hidden. In fact, you may have walked by it and not known it is there.
What do I like about it? Surrounded by four walls, Vasaros Terasa is a calm oasis right in the center of the city. They have lots of great snacky foods which are expertly prepared. One of our favorite is the "coated mushrooms", crunchy deep fried mushrooms bursting with fresh mushroom flavor. There are often live music performances though we have never been there for them.
There are lots of gems in Vilnius serving great food at relatively modest prices. Vasaros Terasa is one of ours. Does anyone have other favorite eating spots they would like to share?