Dressing in costumes is a major part of celebrating Reformation Day. Renaissance/Medieval costumes. Think: princesses, knights (think armor of God), Robin Hood, maidens, etc. I saw a knights kit at Target (in the toy section) for $12. And with all the Halloween costumes in stores, you should be able to find a costume relatively cheap and easily.
You can also go for a traditional monk costume. I made Jack's out a brown turtleneck and a piece of cording.
More on Anne's costume from last year here...Every little girl loves dressing up like a princess and this is a perfect opportunity.
Capes are also very fun and reformation-ish. Simplicity Pattern 5927, is a very easy and simple pattern to follow. This pattern requires very little sewing when you make it with felt (what the pattern actually calls for). You pretty much cut out the cape and the hood and then just sew those two pieces together. Add some ribbons ties and you are done. Plus, with felt recently on sale at Joann's these cost only about $8-9 to make (including ribbon). I altered it a bit for Anne's version (above) to include a lining and the strap and vintage button across the top. I used red velour for hers. Note: Red is the liturgical color of Reformation Day.
Do you celebrate Reformation Day? Any costume suggestions you'd like to add are welcome!