This is done by a svn:ignore property in SVN. This property can be added to a folder.
Let us imagine the following:
+-- root
+-- bin
+-- ...
to ignore the bin folder you have to set the svn:ignore property onto the root folder. First change into the root folder and do the following on command line:
svn propset svn:ignore "bin" .
Or you can do this via TortoiseSVN on Windows (file->properties->Subversion Tab).. Further reading in the Subversion book.