Many times, application developers ask how they can get RDF data from the semantic web into their application, from the recommended syntax RDF/XML. This usually ends up being a question about parsing syntaxes and APIs in certain languages. There are widely available, mature and standards-compliant open source parsing libraries available for most high level programming libraries that application developers might need. This article has provides a summary of what are good choices and up-to-date.
The simple answer is: use one of the readily-available parsers that open source developers in the community have provided. There is no need to create a new parser for the most commonly used application languages, in a similar way to how XML parsers and APIs are widely available.
The more detailed answer depends on the application programming language being chosen (or if a new project, this might influence that choice), as well as the licensing of the project. Most of the items listed below are in easily reusable form and are used in commercial applications. Finally, there is a question of the syntax details - does the system support the latest RDF/XML Syntax Specification (Revised) W3C Recommendation of February 2004.
The list below covers what is available and what I recommend when people ask for commonly used languages for web sites.
For the state of the tools that have been run against the RDF/XML tests, see the RDF Core Test Results.
Several of the parsers above also provide support for other RDF syntaxes such as N-Triples, as used by the RDF test cases, Notation 3 (N3) and other subsets of N3 and experiments such as Turtle.
There are also several other older, unmaintained software or ones with unknown state against the tests that I have no detailed personal knowledge of: Injectilo (XSLT), Profium (Perl and Java, commercial), libwww (C, old), Snail (XSLT, old, slow) RDF Filter (Java, old), Repat (C, old), SWI-Prolog (Prolog), XWMF (Tcl, old) W3C Perllib (Perl).