Graphistry is impressive, but not free, and needs their server and an API key. You probably already know about graphviz sfdp (not interactive). There's been interesting recent work on distributed maxent optimization https://arxiv.org/pdf/1506.04383.pdf and sparse stress models https://arxiv.org/abs/1608.08909 (see its references as well, for example, Khoury's MARS is still available at https://github.com/marckhoury/mars). This problem requires a ton of algorithm engineering, a lot of messy user interface engineering, and integration into an HPC environment is a big issue, so progress in open source has not been that rapid.