2008-09 promises to be an eventful time in Vilnius. Along with Linz, Austria, the city has been designated the 2009 European Capital of Culture, a title which has been passed among EU cities every year since 1985. This title will enable Vilnius to host an extraordinary number of events, including concerts, festivals, exhibits, etc. Here is the link to the main music events, which include the Vilnius Opera Festival as well as festivals dedicated to electronic music, jazz, and chamber music (in addition to all the regular concert seasons in Vilnius).
And from October 24 to November 8, Vilnius will host the 2008 ISCM World Music Days, which will feature dozens of concerts, discussions, and other events, including several premieres by important composers and performers. The full program is available at the above link.