Well, I’ve mentioned uploading via HTTP before, but I must confess, I’d not used the object model. Well, it turns out that it’s just the same as uploading an image (just without thumbnails getting generated…
SPList docs = site.Lists["Documents"];
FileStream fs = new FileStream(@"c:\SomeDocument.txt",FileMode.Open,FileAccess.Read);
docs.RootFolder.Files.Add(docs.RootFolder.Url + "/SomeDocument.txt",fs, true);