Forewarning: While the following suggested material is published by WotC, it should be noted that the contents presented in these articles may only be, effectively, playtest material. It may not been fully refined and may cause unexpected balance issues. It's even been contested as "official" material.
Yes, they are in the Unearthed Arcana.
One of the best examples of this is found in the first feats UA. In this installment, you are given examples with explanations for why each one is bad or good. You can directly use this advice to make your own homebrewed feats.
A less successful UA comes in their Modifying Class installment. They give a good rationale for what to look out for when modifying classes, and what the designers intended for each class to do. It fails in immediately presenting examples that don't follow its own advice (in particular, the Favored Soul).
A ready-made version of homebrew can be found in the variant rules installment. They give you rules for Players Make All the Rolls (beware: the math is incorrect here), Vitality, Custom Alignments.
You also have a UA installment of what players can do during their downtime. These are alternative rules you can put into your game which lend the same effect of "homebrew made for you."
Also, there is the UA on encounter building. While there are already rules for the DMG with regards to building monsters, this tells you how to make encounters/battles instead.
Finally, there is the UA installment of Traps, which instructs you how to make simple and complex traps, how to run them (even using Initiative to do so), why to use them, as well as a lot of premade traps you can readily insert into your games. It goes into a level of detail that the DMG does not have.