We just purchased a bunk bed for out 4 year old. The neat part about it is that it's shorter than a standard bunk (the bottom bunk is basicly on the floor like a platform bed but we'll be using it for out youngest soon so it'll be nice) so I'm way less worried about her falling out of the bed in the middle of the night. It does have the slide and I think my DD with love it. We got ours at a store located in Columbus, OH. I think they do shipping if you're interested in checking out what they have or just to get idea you can visit their web-site. http://www.bunkloft.com/index.html They do just lofts as well if you didn't want the bottom bunk at all.
We had them custom make a full over full bunk with the slide and I can't wait to get it!! We'll be picking it up in two weeks. It's a little family owned business and are so easy to work with. Oh, and when the kids are done with the bunk we'll be able to unstack them and they'll have to nice full sized beds.
Oh, and I just want to put on a disclaimer that I am in no way affiliated with this store I just love their products and can't wait to get out bed! We searched for a VERY LONG time for the perfect bunk and this place had stuff we've never seen before.