In Oracle, people seem to call on some wacky table called "dual" a lot. What the heck is it? Seemed to me to act like an internal temp table, which it turns out is essentially what it is...

Oracle: dual table:

Here's the excerpt from the February issue of Oracle Magazine (SENDMAIL section):

I created the DUAL table as an underlying object in the Oracle Data Dictionary. It was never meant to be seen itself, but instead used inside a view that was expected to be queried. The idea was that you could do a JOIN to the DUAL table and create two rows in the result for every one row in your table. Then, by using GROUP BY, the resulting join could be summarized to show the amount of storage for the DATA extent and for the INDEX extent(s). The name, DUAL, seemed apt for the process of creating a pair of rows from just one.
Chuck Weiss, Oracle

So when you see "dual", go with it, I guess. Hopefully some Oracle mastermind will clue me in a bit better later.