There are some great boutiques, markets and stores for shopping in Berlin. Check out:
Stilwerk, Kantstrasse 17: This design marketplace is located in a small enclosed mall containing four floors of furniture, design and home furnishing retailers. Great to see current European trends. There is a small café for coffee or a light lunch.
KaDeWe, Tauentzienstrasse 21-24: Kaufhaus des Westens, built in 1907, is the largest department store in Europe. The main attraction is the food and gourmet floor with everything you could imagine. A good place for a fast lunch, but is very crowded and noisy.
Kunst und Trodel Markt, Strasse des 17 Juni, Tiergarten: This a Saturday-Sunday market that stretches west of the S-Bahn Station. It is a fun place to spend a few hours looking at early 20th century antiques, furniture, books and records.
Hugo Boss, Rosenthaller Strasse 49. Check out the great design of this store. It was down the street from my hotel.