The "par" system
Taking this in mind, you can put together a very simple formula for a team to reach the .500 mark at the end of the season. First, a team needs to split every 2 and 4 game series, whether played at home or on the road. More interesting is what "should" happen in the more common 3 game series. At home, teams should win 2 out of the 3, and on the road, teams should win 1 out of 3. If they do this, they will finish right at .500, with an 81-81 record.
It seems, then, that more information can be provided about how a team is doing, relative to how they would have to play in order to finish .500, by adding another line to the team's record. I call it "par" just because it's convenient to do so. Finish a 3 game home series with two wins, and you "parred" the series. If you utilize this basic idea, you can determine whether a team is really in as bad of shape (relative to .500) as it seems.
The Twins provide an excellent example. They are currently 7 games under .500, and fans may be frustrated. However, they are only 1 under par (or if you insist on following through with the golf analogy fully, 1 over par). They've played more series on the road, and this extra statistic shows that, partially explaining why their record is under .500.
It's only a novelty stat, and doesn't add much, but it's something that I like. I've been tracking it for the Twins all year, and may comment on it from time to time.
Incidentally, it is my belief (though I have not run any tests on this using past results), that it is easier to win a second road game over a 3 game series than it is to sweep a home series. As a result, in order to finish over .500, it is probably easier to play consistently well at home and on the road than it is to play supremely well at home, and only do what you are supposed to at home.