Agree with Pabst. Exchange traded 3m forward rates are a good place to start.
For longer term analysis you will need to avoid the discontinuities caused by changing contracts. You can do this by log-linear interpolation to obtain constant forward rates. e.g. a constant x_mth rate, y_mths forwards. Can easily be done in excel once you have the underlying data....
If you have access to a bloomberg terminal you can also compare bond yields. Generic bond yields with constant maturity are best. An even better approach would be to compare swap curves (spot and forward) in the various currencies.