I'm in southern Germany (near the Swiss-French border) and have been for 13 years now. You won't be able to get everything like you're used to but what you need to bring along depends on what you're accustomed to using and where you'll be located. Of course things are also available online, but be prepared to pay quite a bit for them. If you're military, you'll have good sources for a lot of things (so I've heard) but otherwise there will be a few things you might want to stock up on.
The baking powder you get at stores here is single-acting, not double-acting like in the States. Bring some along - you'll be happy you did. (took me forever to find out that bit of information!) It can also be found (or special ordered) at some Asian supermarkets. I make IMBC and have my parents bring/send some cream of tarter from time to time. Next time I need it, though, I'll probably see if I can get it from the pharmacy. They wanted me to bring the old package next time so they can see exactly what's in it. Bring along some baking soda, too. Some stores have started carrying little Arm&Hammer boxes but most places still have tiny little packets which are really annoying to use.
Crisco is available in some stores although it's a tiny tub which costs quite a bit compared to what you're used to. I just use it for greasing up tools and making cake release so I make it last. Vanilla is different here. I can get US-style vanilla aroma from France but it's one thing you might think about bringing, too.
Anything that's purely a cake-decorating supply will probably be hard to find (or expensive to have shipped). Tell us what you use regularly and we can point you in the right direction, though.
I have a good source for reasonably-priced fondant but it can also be ordered online for a bit more. You wouldn't want to haul any buckets of that over on the plane!
If you make MMF, marshmallows are now readily available nearly everywhere. Powdered sugar might be different than what you're used to - you have one type to choose from here and I have no clue if it's 6X or 10X or what - it's powdered sugar, plain and simple. Grocery stores generally carry less variety than in the States so often you just have to make do with what you find.
I've also heard that the flour is different but since I didn't bake in the States, I really don't know. Forget cake mixes, though. The ones here won't be what you need. No corn syrup, either. (at least none I've found)
I'm sure there are lots of other items you'll miss but I think those are the big ones.
Let us know exactly what you use the most and we can tell you more! Plus once you're here and realize you can't find something basic, we might be able to steer you in the right direction.
Good luck with your move and enjoy Germany! It's a great place to live