For communicating with people back home, cell phones are cheap and easy to buy, even for a short trip. But the best deal is to make phone calls via the Internet. If both parties have iPhones and access to Wi-Fi, you can enjoy a FaceTime connection across the street or across the ocean for free. Otherwise, Skype is a good and inexpensive standby.
One recent development in Europe is the advent of free walking tours. While the tour technically doesn't cost anything, guides work solely on tips (and they make sure to remind you of that). At first I wasn't hot on these "free" tours, as guides--generally expat students who have memorized a script--emphasize stories over the strictly academic and are known to take some liberties with historical events and characters. But they're still enjoyable, and for travelers on a budget, they provide an affordable way to get to know a place.
One thing I always encourage young travelers to do is to keep a journal (or these days, a blog). As a travel writer and teacher, one of my favorite discoveries is that the journal entries I wrote as a scruffy 20-year-old in 1975 still resonate with the generally much-less-scruffy 20-year-old American exploring Europe in the 21st century. Today the same timeless magic is there--it’s just a lot more convenient and comfortable to find it.
Rick Steves (www.ricksteves.com) writes European travel guidebooks and hosts travel shows on public television and public radio. Email him at email@example.com and follow his blog on Facebook.