(partially free) UML modeller plugins for Eclipse I found:

• Omondo Eclipse UML is a modeling tool offering simultaneous round trip and an XMI repository, simultaneous synchronisation between java code and class diagram and has a SVG export feature – there's a free edition and an enterprise version for $1500/developer
• Slime UML is a slim and fast UML tool focused on documenting code or reverse engineering – a license cost EUR 30 and offers WMF and SVG export, not too much money for essential documentation features
• Visual Paradigm UML offers Eclipse integration now and exports to SVG, PDF, HTML and even OLE and some promising feature-buzz about Model Assist to help you to reuse existing model easily, the rectilinear connector support (to avoid spaghetti in your diagram) – costs are 838.5 $ for the prof.version including Eclipse integration and annual maintenance of 139.5 $

All of these tools offer a free "community" edition – so worth a try anyway.