Here's some grammar activities that may be quite useful for b1 and b2 students. The first three links are rephrasing exercises.

http://www.box.com/shared/lx5hicgs0i
http://www.examenglish.com/FCE/Use_of_English.htm
http://www.ompersonal.com.ar/firstcertificate/contenidotematico.htm
http://www.examenglish.com/TOEFL/toefl_structure_http://www.ompersonal.com.ar/firstcertificate/contenidotematico.htm1.htm
http://www.examenglish.com/leveltest/index.php
http://www.examenglish.com/ECPE/ecpe_grammar.htm
http://www.examenglish.com/grammar/B1_reported_speech.htm
http://www.examenglish.com/ECCE/ECCE_grammar.htm