Distribute copies of any kind of reading text according to the level of the class.
First, let the students read the text. Then, ask them to take a coloured marker and colour as many ocurrences of a certain consonant blend as possible (for example, "sp"). Give them two or three minutes to perform this task.
Make them count the ocurrences. The student with the correct amount wins a point. Repeat the activity with another consonant blend and using a different colour.
A variation if this activity consists of making the students mark all the nouns with one colour, then the verbs with another colours, the adjectives with a third colour and the adverbs with a fourth colour. Again, make them count each category and the student who gets the correct amount wins