hi,
i just went to prague about a month ago. it was realy beautiful but it is sooooo touristy. British everywhere and all they do is go there and drink stoopid amounts and, well i wouldnt go as far as saying ruin the culture, but it definately puts a damper on it. Saying that the castles are awsome and the ppl are fantastic (and beer cheap).
If you have limited time i would suggest checking out some festivals. I went to Sienna for Il Palio, and it was the highlight of my trip (in july). Running of the bulls was NUTS (end of july). and bastille day in paris is mad as they have an awsome fireworks display to music off the eiffel tower, and everything is very french (early august i think). i didnt go to tomatina, the big tomato fight, in spain (aug 30) but ive heard its awsome.
Other places id reccomend are barcellona for shure, um if your into extreme stuff go to bovec in slovenia, i did canyoning paragliding and ww rafting there and its absolutely beautiful and cheap and FUN.
I didnt get to much of eastern europe but it sounds awsome and cheap. Dubrovnik in croatia was cool but a bit too touristy for my liking. Awsome history though in the old town.
Well thats about it from me. Travelling by yourself should not be a problem. Ive done most of this by myself and never had a problem (except having my wallet nicked right out of my pockets in italy) but im not a girl and i wouldnt have done some things if i was. (girls arent allowed to run with the bulls).
anyway have fun and get out there, europe is AWSOME. Next stop for me is thailand.YAY.