A classic situation would to attach these close-up filters to a longer telephoto lens to allow the image of the flower to fill your viewfinder. This is an excellent, inexpensive option to travel light. Note that the sharpness of the images will be compromised and you'll see more softness in the corners of the image.

The filters often come in sets, with diopter settings of +1 through +7 (a diopter is a unit that designates the refractive power of the lens). A common set is +1, +2 and +4. When stacked, you must have the strongest filter closest to the lens for it to work as intended. Pricing runs from $15+ for a single one, to the better Hoya, B&W or sets at up to $60-70.

The results I have seen from the Canon close up filter are quite good.

Reversing ring
A reversing ring is a threaded adapter that lets you mount the lens backwards on the camera body. The downside is that you expose the lens contacts, etc. to the elements, and you lose all metering capabilities. This option is best used with a lens that allows you to adjust aperture and focus manually. Roughly $5-20.

Extension tubes
Extension tubes are similar to lenses, but without the glass (elements), as shown in Figure A.

FIGURE A

This extension tube looks like a lens, but there's no glass. Click picture for a larger image.

What this simple design does is move the back of the lens further away from the sensor or film plane. The drawback is that less light reaches the film/sensor, so the shutter speed drops, and longer exposure times are needed if you don't use faster film or higher ISO settings.

The best analogy I can provide is this: like a projector, the further you move it away from the display area, the larger the image gets. It's simple, yet very effective. They are also much lighter, since there is no glass in the tubes.

This option can be cheap to moderately expensive, depending on the features of the set. The cheapest manual focus (MF) versions can be had for about $20. The full auto-focus (AF) versions made by Kenko will run $130 or more for a new set. The aforementioned set is quite possibly one of the better options.

Figure B shows the disassembled extension tube set.

FIGURE B

Here's what the extension tube set looks like once disassembled. Click picture for a larger image.

Bellows
Remember older cameras that had the accordion-like hoods between the front of the lens and the camera body? This option is difficult to use, and very cumbersome. The difference between it and extension tubes is the adjustability of the setup.

Another downside is that it can be somewhat front heavy, so your tripod head must be relatively strong. Not a recommended setup, given the other lighter and more flexible options available. If you still want to try one, they can be had online for around $80-$100 or more.

Macro focusing teleconverter
A macro focusing teleconverter is similar to an extension tube, but it's got glass, as shown in Figure C.

FIGURE C

Here's a macro focusing teleconverter. Click picture for a larger image.

As with an extension tube, less light will reach the film or sensor, and a longer exposure time will be needed. However, working distance remains the same as without the teleconverter.