The Federal Employment Agency (Bundesagentur für Arbeit) offers a good database for vacancies. It comes in several languages, however, the search words should be the German equivalents because most German employers do German job offers only.
Also a possibility: EURES. EURES is committed to promoting the mobility of job-seekers in Europe by providing advisory and job-finding services. EURES offers interesting job prospects and funding programmes.
There are specific websites which focus on job offers for English speakers:
The biggest job search engines are
Another possibility is utilizing the social networks (e.g. Xing) for companies that are in search of your particular knowledge. Expat forums like Internations and ToytownGermany are often useful platforms for job seekers.
CONTACT RECRUITMENT AGENCIES
This strategy enables you to benefit from the large recruitment agency network; however, it can also be difficult to find the "right" agency and one that you can rely upon to put your needs first. You should never have to pay a ‘fee’ for using a recruitment agency, so be aware and do not use any company which asks you for payment. The key to using recruitment agencies is to be specific with the type of job you are looking for, including salary, location, working hours, responsibility, etc. This will help you narrow your search and choose the right agency.