All Posts With A Tag Within a Category or Post

I have a post that’s a “summary” post of sorts. Within this post, I want to link to all posts that have a tag. So I need to:

1) Get all posts that have a tag, to iterate over; and
2) Print them out (the title, and link to the post).

How do I do this? I tried messing around with get_posts, but that’s not really for this, it’s for my main loop… (I have runPHP, and I’m using that to iterate.)

Similarly, I have a category that only has a few posts (maybe 10-20); I want to get the titles and post-slugs for all those posts. How do I do this? Maybe there’s a plugin for this?