Batik from Apache offers a viewer called Squiggle which provides very good support for SVG 1.1. A useful feature is that it provides an export facility to image formats that can be useful.
Another useful module converts Truetype fonts to SVG.
Batik offers a good reliable alternative to the current set of browsers at rendering SVG documents. Often comes in useful when checking whether your SVG code is wrong or whether the browser does not provide the correct support.