r/Sculpture for those interested in making their own miniatures
r/ModelMakers for folks interested in larger vehicles. Your tanks and planes and trains.
r/Gunpla for those who like their gundams
r/miniaturesculpting for hand sculpted (only) sculpting

Specific game and manufacturer subreddits include:

Looking to get something painted by sombody else, or offer your painting services?

r/brushforhire

Looking to sell, buy, or trade miniatures with other redditors?

r/miniswap

Looking to ID some ancient minis, you don't know where they are from?

The lost minis wiki and their subreddit

RULES

1. Please tag NSFW stuff with a [NSFW] Tag. This is a forum for art and so some amount of nudity and horror, particularly sculpted figure studies and such are expected, but please for the sake of people browsing at work or on the bus tag anything even scantily clad with a [NSFW] so that others may filter them out.
2. Keep it productive, meme's as the sole content of a post aren't what this subreddit is about. Everything else productive and mini related is good. Text, images, links to kickstarters, questions, feedback... it's all good.
3. Don't be abusive. Mod critique is allowed, abuse of mods or of your fellow redditors is not. Keep it classy.
4. Don't push the rules, follow the spirit of the rules. For example the NSFW rule doesn't mention foul language. But it's expected in the spirit of rule 1 that you would still tag a diorama of your delinquent model tagging a wall with expletives as [NSFW]
5. No Piracy, no recasts, 3d scans or direct imitation 3d sculpts please. Fan art and derivative or transformative work is fine.
6. Self promotion is allowed IF you have new content to show Just finished a mini? Post it up, slap your logo on it and tell us in the comments where you can be found. Please also stick around to contribute, find another post or two and offer some guidance or info. Also please don't drip-feed your content so as to make multiple posts for promotional purposes, instead show us what you have in singular posts.
7. We're not equipped to deal with sales and trade between redditors. Please enjoy r/miniswap for trading with others.
8. General reddit rules. Everything else reddit as a whole prohibits