Implants enhance S.P.E.C.I.A.L attributes in Fallout: New Vegas. There are a grand total of 9 Implants. There's one for each SPECIAL attribute, and there's also one that gives +4 DT, and another that gives minor Health Regen (+1 HP every 10 seconds). The Health Regen is useless in combat, but once combat is over, you can wait for 24 hours to restore your health to full.
All Implants are found at the New Vegas Medical Clinic. The SPECIAL ones cost 4000 Caps each, the DT one costs 8000 Caps, and the Health Regen costs a whopping 12000 Caps.
Source: swk3000 forum post