Portraiture, Architectural and Macro
Portraiture: short zooms work best for portraits. A 24-105 zoom is a nice choice since it's wide enough to handle a family portrait but long enough at the telephoto end to serve as a nice focal length for an individual portrait.
Longer focal lengths can also work well for portraiture though as their increased reach tends to flatten facial features in a way that flatters most faces. Portraits can be made with wide angle lenses too, but must be done very carefully to avoid a fun house mirror effect.
Architectural photography: if you're serious about shooting buildings (especially big ones) a tilt-shift lens is your first choice (if you can afford it). These pricey optics can be manipulated to correct for "Keystoning" a problem that occurs when the photographer has to tilt their lens up to get the whole building in the shot. This is the effect that makes it look like the building is falling away from the camera. If you can't afford a tilt-shift lens (usually around a grand a pop) then use a wide angle lens and leave enough margin around the building to allow for correction in an image editing program such as Photoshop (hmm, sounds like an idea for another story).
Macro photography: almost any lens can be pressed into service for macro or close-up photography, especially with the use of tools such as extension tubes, macro add on lenses, bellows, reversing rings, macro couplers and other accessories. Generally longer focal lengths keep you farther away from your subject, which is nice when you're shooting things that sting, or don't want to accidentally squish your subject as you get close. If macro photography seems like it's your thing, then an honest to goodness macro lens and not a regular lens with close focusing capability can be a solid investment. How do you tell a real macro lens from an overhyped one? Well, real macro lenses tend to be fixed focal lengths or "prime" lenses while close focusing lenses tend to be zooms.