Gephi was already mentioned, but I’ll incode screenshots and a short description here.
Gephi can not just visualize graphs but also supports analyzing, layouting and further importing and exporting. There is a Semantic Web Import Extension that allows you to directly query (via SPARQL) or import RDF data. https://wiki.gephi.org/index.php/SemanticWebImport (You can install it directly within the program at Plugins.
There’s a JavaScript Graph Visualisation Library which worked quiet nice for me: http://sigmajs.org/ It works well together with Gephi since you can Export your graph from there and import the file into SigmaJS. That way you can export your graph to an interactive web site. Example: http://fannon.de/p/smw/vis/George_Orwell_Platz_30.html
An important mention would be D3.js which has already dozends of force graph examples. But it doesn’t support RDF directly, so the data has to be converted first.
A nice one is this: http://nylen.tv/d3-process-map/graph.php?dataset=les-mis
