This gall caught my eye, ditto this one here. It was early fall and it looks as if the moth had already emerged through its beveled emergence hole. See the Hilton Pond Center for more about their interesting lifecycle.
Searching the internet I found a most interesting paper Host-associated genetic differentiation in the goldenrod elliptical-gall moth, Gnorimoschema gallaesolidaginis (Lepidoptera: Gelechiidae). Clearly these goldenrod galls have been evolving for a very long time. To me it has been fascinating to learn about this interesting ecosystem in a herbaceous plant. I've known of galls only in shrubs and trees.
Let's keep an eye on the tantalizing research interests of John O. Stireman, in particular the spindle-shaped gall half way down this page.