Finding An Apartment

Here are some links for sites that list apartments in Berlin.

Property Managers:
http://www.degewo.de
http://www.taekker.de (These are the people we're renting from)
http://www.ca-m.de/

Advert Sites:
(Note: Some of these sites charge commissions- check the site for details!)
http://www.wg-gesucht.de
http://mopo-immonet.berlin1.de
http://www.studenten-wg.de
http://mieten.immonet.de
http://www.immobilienscout24.de
http://www.rooms-in-berlin.com/
http://www.immowelt.de/

You can also find places by putting an ad out and/or reading the ads in the papers immobelien, zitty, and the local paper. Zitty and Exberliner are also online. Craigslist is an online classifieds site that we used all the time in the states. Here it's sometimes used, but usually for sublets / shares. Expatica is a great site for getting solid information. Unfortunately not many use their classifieds section.
http://kleinanzeigen.zitty.de/
http://cgi.xberliner.com
http://berlin.craigslist.org/
http://expaticade.franglo.com/classifieds

Other ways to get a place:
If you're desperate you can always go through a rental agency. I've heard this can be pricey, but is worth it as they do all the work for you- narrowing down the thousands of available empty apartments in Berlin to just one. Here are some I've found / been recommended to:

-Claudia C. Rehberg
Managing Director
Professional Organizing Relocation Consult GmbH
Post: Wiesenstraße 18, D-65843 Sulzbach
T: +49 (6196) 5946 12 F: +49 (6196) 5946 71
Mail: c.rehberg@proforg.com

http://www.progedo.de/41-1-press-articles.html
http://www.steptoberlin.de/aboutus.htm
http://www.first-relocating.de/

More about relocation agents here: http://www.expatica.com/de/housing/relocation/what-can-a-relocation-agency-do-for-you--571.html