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.