Last year I wrote about divine "portfolios" and how they're a lousy starting-off point when you're designing a divine pantheon. I made the point that "gods can have overlapping portfolios, and the more important ones can have a grab-bag of domains with only obscure connections between them."
Recently I decided to map out some of these "obscure connections" using software called Scrapple. You can see the last draft below (click for a larger version).
In most cases the connections should be obvious; others are more obscure. (For example, the Greeks connected "the sea" and "horses" because crashing waves supposedly resembled galloping horses.) More items and connections can be added to the diagram.
What you might do, when designing a pantheon, is to draw a polygon around a set of connected "portfolios" and then assign them to one god or another. (So for example, you could have a Dwarf god overseeing the Earth, the Underworld, Metals, Blacksmithing, Crafts, the Community and War.) Do that for each of your major deities, and don't worry too much about overlap.
This diagram could also be used in an RPG where each player is a god. As they go up in level they could take over nearby portfolios, making the lesser deities of those areas their "aspects" or followers. Turn your Rudra into a Shiva with a lengthy divine quest-line, in other words.
- Con-Myth: The Portfolio Cloud