I've created some exercises about Spanish accents rules. If you want to review the grammar, you can find it here: Spanish accents Rules.
(Scroll down to see the answers)

Exercise 1.:
Write the following words on a paper (or your computer) and explain why do they take accent or not.

a) patata b) jamón c) rotura

d) lápiz e) máquina f) silla

Exercise 2.:
Choose the right option (there are only two right options):

a) cócina b) tazá c) razón

d) papél e) sofá f) dísco

Exercise 3.:
Read the following sentences and choose the right option:

La casa --(a)-- abandonada.
a) está - esta - ésta

El --(b)-- es grande.
b) camion - camión - cámion

Tengo una --(c)-- roja.
c) lampara - lámpara - lampará

El --(d)-- pasa a las dos y cuarto.
d) autóbus - autobús - áutobus

Me gusta mucho comer (e).
(e) jámon - jamón - jamon

Recommended material:

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Puerta del Sol - Audio Magazine

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Angeles' Blog "Spanish Word of the Day"

Visual Link Spanish

Learn Spanish with donQuijote.org

Answers:

Exercise 1:
a) patata --> No accent because it's a "llana" word, ending in vowel.
b) jamón --> With accent because it's a "aguda" word, ending in "n".
c) rotura --> No accent because it's a "llana" word, ending in vowel.
d) lápiz --> With accent because it's a "llana" word, ending in letter different from vowel, n or s.
e) máquina --> With accent because it's a "esdrújula" word.
f) silla --> No accent because it's a "llana" word, ending in vowel.

Exercise 2:
Right options: c) and e)

Exercise 3:
a) está
b) camión
c) lámpara
d) autobús
e) jamón