Shamus (over at Twenty Sided) has posed an interesting question. Given that I could travel through time, and was sure I'd wind up somewhere in Europe between 1000 CE and 1300 CE and I could only carry a loaded suitcase. Assuming a normal sized checked bag on an airplane, this is my list.
1. A monk's cassock. When in Rome, do as Romans do. A monk is essentially untouchable, and it gives me an excuse not to talk in the form of a vow of silence. This would be a little bit better lined than your typical rough spun cassock, but it would look like one. That's the important bit.
2. An AKS-74U Carbine with folding stock, and some ammunition. I hope never to have to use this, but I think it goes a long way.
3. A faked (the book of genesis might actually be real) bible, in Latin, with a compartment holding the following. Please remember that bibles were copied by hand and would be rather heavy, so holding all of this would not be considered strange.
4. Antibiotics. I'd update my vaccinations before heading off on my time trek, but you never know.
5. A netbook (essentially a small computer capable of surfing the web an not much else.) Pack some reference material onto this get going.
6. A spare battery. For the netbook.
7. A hand-crank LED flashlight. If I travel by night, fewer people to see me.
8. A butterfly knife (this is a knife that folds into it's own handle. Very neat.)
9. A few flints and some tinder. Obvious reasons.
10. A box of strike anywhere matches. Once again, obvious.
11. A swiss army knife. Seriously. You have to ask?
12. Some accurate maps of Medieval Europe (geo-physical, geo-political, by language spoken)
That's all in that bible.
13. The gear, chains and pedals from a bike and a few other odds and ends to make a generator. This should make sense given the netbook.
14. A small canvas bag with some gardening supplies. If I can get a decent crop going, I should be able to go vegetarian. This saves the trouble of things like gutting and cleaning meat. Most vegetables can be eaten raw.
15. Some food.
17. A parachute cord braclet. Parachute cord is sturdy stuff. These braclets can hold quite a bit of it, and rope is useful.
18. Some parachute material. Once again, sturdy cloth.
19. A plastic tarp and a funnel. For collecting water, and possibly for keeping it off my head.
20. A solar blanket. Obvious again.
21. Salt and honey. They're preservatives and they might help with a few things, either put to their medieval use or for trade.
*22. Some jewelery. Nothing too fancy that might give me away.
23. Some actual medieval clothing for when I get set up.
The plan goes something like this. Learn some latin. At least I won't have to be mute
Land in Europe, whenever.* Put on my cassock. This should keep me from being attacked. The wrath of god and all that. Using my map, go find the nearest place where I can steal a wheelbarrow and some fertile soil. Go find a nice cave to hole up in and become a hermit. Being a hermit, I can avoid things like plagues and witch-hunts and no one will bother me. W00t.
*Alternate plan, if appropriate. masquerade as a monk to get across land. Find a city and change into some decent clothes. Sell some jewelry to make myself a start, and then find a post teaching at a university. If all goes sour, revert to plan one.