Most lens makers offer more than one macro model, so while this isn't a comprehensive roundup, it will give you an idea of the range of options available to you.
Canon EF 100mm ƒ/2.8L Macro
Nikon AF-S DX Micro-NIKKOR 40mm ƒ/2.8G
Olympus ED 50mm ƒ/2.0 Macro
The Canon EF 100mm ƒ/2.8L Macro IS USM features Canon's Hybrid Image Stabilizer technology, which compensates for both angle and shift camera shake, ideal for handheld macro photography. As an EF lens, you can use it with both full-frame and APS-C-sensor Canon cameras, though it will frame like a 160mm with the latter. Estimated Street Price: $1,049.
Nikon offers several lenses with 1:1 macro capability, the newest being the AF-S DX Micro-NIKKOR 40mm ƒ/2.8G. Designed for use with Nikon's DX (APS-C) sensor cameras, it offers continuous autofocusing from infinity to 6.4 inches. With a 35mm-equivalent focal length of 60mm, it's also a good choice for portraiture. Estimated Street Price: $279.
With a fast ƒ/2.0 constant aperture, the Olympus ED 50mm ƒ/2.0 Macro frames like a 100mm on a full-frame camera. Pair it with the EX-25 extension tube, and you get the 35mm-equivalent magnification of 2x. This lens can be used with both E-System and PEN System cameras (with the optional MMF-2 adapter). Estimated Street Price: $479.
Panasonic Lumix G Leica Macro-Elmarit 45mm ƒ/2.8 ASPH
smc Pentax D FA Macro 100mm ƒ/2.8 WR
Sigma 105mm F2.8 EX DG OS
Designed for use with Micro Four Thirds system cameras (including Olympus PEN models), the Panasonic Lumix G Leica Macro-Elmarit 45mm ƒ/2.8 ASPH has a 35mm-equivalent focal length of 90mm. It also features Mega O.I.S. optical image stabilization for handheld close-ups. Estimated Street Price: $679.
For Pentax DSLRs, the smc Pentax D FA Macro 100mm ƒ/2.8 WR is designed for durability, with an aluminum housing and weather sealing to match Pentax weather-resistant bodies and Super Protect coating on the front lens element to repel dust and water. It frames like a 150mm lens (35mm equivalent) and can focus as close as 11.9 inches with 1:1 magnification. Estimated Street Price: $599.
Designed for use with full-frame digital cameras, the Sigma 105mm F2.8 EX DG OS HSM Macro also can be used with APS-C-sensor cameras with an approximate 35mm-equivalent focal length of 150mm. Focus as close at 12.3 inches with 1:1 magnification. The lens is available in Canon, Nikon and Sigma mounts and features Sigma's OS Optical Stabilization. Estimated Street Price: $969.