Your local university library will have some journals that might be worth looking into.
How to proceed?
While reading papers that you have already found, take notes about the contents of the paper and highlight interesting citations you want to pursue. It is very useful to create a citation file in http://en.wikipedia.org/wiki/BibTeX BibTex format to maintain your bibliography.
When done reading, look up the citations in the reference-section of those papers. Pursuing this web of citations will lead you backwards in time to uncover layers of foundation, contrasting and related work.
Try to see which papers cite papers you have read. This is called a forward search.
Use the names of people that wrote good papers to find their web-pages and have a look at their publication lists.
Search for departments of important universities that work in the area of interest.
Try to find reading lists on your topic.
Identify the common conferences and journals that are used in your area.
Go and talk to or email people that do research in the area you are interested into.
Use search engines:
DBLP
Citeseer
Google
Hints
Google allows restrictive searches by file-type. This is especially useful when searching for papers or slides as scientific publications mostly come as pdf or ps documents. Example queries:
"GPL preamble filetype:pdf" returns a pdf version of the General Public License .
"knowledge management filetype:ppt" returns almost exclusively introductionary slides into the topic "Knowledge Management".
Looking for books
It is often a good idea to have a look in mature research literature to get a basic understanding, an overview, or just definitions. You can find out book titles by looking into lecture slides or asking your professor. When you are looking for a specific book title, follow these steps:
Finally, contact the library staff at the Information Center (Informationszentrum) by email, phone, or personally. This can be very helpful to get information about further resources you may use for your search. These people are experienced with all the available catalogs and databases.