Well, modernity is encroaching almost everywhere, but you can get a bit of a flashback in the Lithuanian countryside. While Vilnius, Kaunas and Siauliai and the other major cities are rapidly catching up with the present, throughout the countryside you can still see people farming with horse- or human-drawn plows, planting and gathering by hand, that kind of thing. A lot of the local craft traditions are still practiced (there's a black pottery studio in Vilnius, lots of weavers, woodcarvers, iron smiths, etc - both in the city and out in the country). There are also a lot of song festivals, at which you'll see your fill of traditional costume, eat typical food and hear beautiful and ancient songs.
Lithuania was the last country in Europe to adopt Christianity, in about the 14th C, so the traditional pagan ways are much more firmly ingrained and to some extent still practiced in the daily life of modern Lithuanians, and even their Catholic religious observances are informed by these local traditions.
At Rumsiskis (Room-shish-kiss), there is a fantastic outdoor museum with a large display of traditional architecture, and you can see craftspeople practicing their art with traditional tools and materials. Linen, amber, silver, woodwork, black pottery and iron work are typical of these crafts.
Near Kedainiai there is a church and collection of outbuilidings at which a priest has assembled a tremendous collection of religious artefacts - mostly beautifully embroidered robes and finely wrought iron crosses.
In Aukstatija (Auk-shta-tee-ya) National Park, people live and farm in the traditional ways, there is a bee-keeping museum and two small villages which are preserved (and lived in) in their old (pre-electricity, running water) state. Pretty well anywhere you go in the country, you'll see people carrying on their lives in much the same way as their forefathers, but this isn't a pretty little history tableau - you won't necessarily find people in native costume (though you might) - it's just day to day, a fairly hard life.
We lived in Lithuania for two years, and of all the places we've lived, it truly became my second home, so I'm totally biased in favour of it, and I've been known to ramble on about it for ages - if you add it to your list, by all means, ask questions!
If you want to read a series of novels about the Baltic culture at the time of the clashes with the Prussians, you might be able to track down the "Tales from the Baltic" series by Skomantas. I believe there are only 5, there might be a sixth:
The Captive,
The Fen Wolf,
Blood Wedding,
The Blue Raven and
The Flaming Tower. They're kind of cheesy, but an easier read than most of the history books I've read on the subject!
Contact Vilnius Tourism office to get info about folk festivals and special events, there's buckets out there.