General

All purpose clinical calculator from CEBM:  diagnosis, therapy, harm
 

Sensitivity, specificity, predictive values, LR's with confidence intervals (ms excel)

Determine sens, spec, LR's, predictive values without CI's: also allows you to work backwards, generating a contingency as well as LR's and PV's from known sensitivity, specificity and prevalence

Sens, spec, LR's PV's (no CI's on LR's) from the center for Evidence Based Medicine.   Includes an interactive LR nomogram for determining post test probabilities from pre-test probability and the LR.
 

ARR,  RRR, OR  and NNT with confidence intervals   Nice calculator however it gives, RRR not RR (which you can then calculate yourself)  It can also be easily applied to studies about harm.

95% confidence interval calculator     (Requires MSExcel)