There are many different kinds of squash and which ones are good for your dragon has already been covered. Pumpkin is a squash too and probably the most widely known squash in western societies. Can't recall if it's good for a dragon to eat though.
Knowing some grocery stores don't always label their squashes the same way, decided to give descriptions of what good kinds of squash to feed bearded dragons look like. I can't guarentee though that I am correct as I don't eat alot of squash nor buy them for my dragon. I don't see a point in buying a large vegetable only to feed a small portion of it to my dragon and having the rest go to waste. But I only have one dragon right now.
Acorn squash- these are typically green, about 6" in diameter and have ridges all the way around
Butternut Squash: quite large, about a foot long. Looks like a large smooth peanut.
Pumpkin: Huge squash, comes in all sizes from 6" diameter to 60" (well doubt you would see them this large but the record sized pumpkin is huge!)
Spagetti squash: medium oval squash, yellowish in colour.
That's all I can think of off hand and are pretty much the ones I am familier with. The only other squash I can think of is an eggplant which looks like a large purple teardrop. It pretty much stands out compared to other squashes. Don't know if dragons can eat these though. Oh and don't confuse ornamental gourds as squashes though, these are not intented as food, hence the name.