Modal verbs

Here you can find some information and exercises on modal verbs along with the key for the exercises. (Source: English Grammar in Use. Intermediate by Raymond Murphy)
Here you can find more exercises on modal verbs.

Conditionals

Here you can find some information and exercises on conditionals.

Here you can find information and exercises on the same topic along with the key for the exercises. (Source: English Grammar in Use. Intermediate by Raymond Murphy)

Here you can find more mixed exercises on conditionals as well as other linking words that can be used in conditionals. There are also some exercises on expressing wishes.