Venus Optics' 100mm F2.8 Ultra Macro lens is now available with Pentax K mount, new stepless EF mount version also available: Digital Photography Review
Tamron 90mm 2.8 SP Di Macro vs Tokina 100mm 2.8D Macro - YouTube
Amazon.com : Tamron AF 90mm f/2.8 Di SP A/M 1:1 Macro Lens for Canon Digital SLR Cameras (Model 272EE) : Tamron Macro : Electronics