Dear Lazyfedi, can anyone recommend a software tool for hand-directed graph layout?

If I have a graph (say, of a finite state machine or something), I can write it in Graphviz DOT format and feed it to xdot, which will do a complete job of layout: decide where the nodes go, figure out some nice curved paths for the edges so they don't go through other nodes or cross over too often.

But if it doesn't do a good enough job, I don't know of any way to slightly tweak its output. As far as I know there's no way I can overrule its decisions about where to put the vertices, but still have it do the rest of the job for me like drawing all the edges. If I'm not 100% happy with its own choices, I have to do the whole thing myself instead.

Anyone know of a good interactive tool that will let me drag the vertices around, and automatically move the edges with them?