Siggraph is a simple perl script to generate dot format files which draw graphs representing the relationship between signed GPG keys, and gives some indication of the 'level of reliability' of indirect keys.
The primary key specified is highlighted in Gold, with keys signed directly by that key are Green. Keys which are then signed by those signed keys have a Green border, indicated some degree of trust. Revoked keys are drawn as red 'stop signs'. Arrows run from signer to signee.
Siggraph firstly creates a temporary keyring in /tmp/keyring.ID (where Id = primary key), and downloads the specified key from the keyserver to this keyring. Depending on the depth requested, it then recursively fetches keys for those signatures on the keyring marked as 'User ID not found'. Optionally, an existing keyring can be specified, in which case that keyring is refreshed from the server, but no new keys are downloaded.
Having ensured you have perl and graphviz (or springgraph) installed:
Download siggraph.pl (right-click and choose Save As...)
Run perl siggraph.pl to see the options.
Example usage: perl siggraph.pl --depth 2 AB123456 |neato -Tsvg >output.svg
-d|--depth - Depth to recurse through key (defaults to 1, depth greater than 2 can be very slow!)
-k|--keyring - Use a specified keyring (won't update from keyserver)
-b|--black - Black & White Output
-v|--verbose - Show debug information
-h|--help - This help screen