Solvent

Dielectric Constant

Protic?
Hexane 1.9 (Nonpolar) No
Diethyl Ether 4.3 No
THF 7.6 No
Acetone 21 No (but mixture with water is!)
Nitromethane (CH3NO2) 36 No
DMSO 47 No
Acetic Acid 6.1 Yes
Formic Acid (HCO2H) 57.9 Yes
tert-Butyl Alcohol (tBuOH) 12.5 Yes
Ethanol (EtOH) 24.5 Yes
Water 78 Yes
A paper providing (too much) details on comparing rates of nucleophilic substitutions in different solvents: Parker, A. J., Chem. Rev., 1969, 69, 1-32. See particularly Table VIII, pp. 13-14.