Putting posts into array

I have a question. I need to put posts into an array, so I can display them later in the page, outside the loop. Here is my scenario…

I have a top 5 stories column, this is inside the loop. The last 25 posts go into a navigation box. This navigation box has four categories. Something like: Cats, Dogs, Cookies, Foobar. Now if a user clicks on Cats I want only posts to appear if they have been tagged as ‘cats’. And so on and so forth. I already have the navigation box coded so I don’t even need to worry about that, but there are div boxes, and stuff like that separating the categories, so I can’t have it inside the loop otherwise it’ll get screwed up.

So I want to know if there is a way I can put the posts into category arrays inside the loop so i can just print them outside the loop in my navigation box. Any ideas?