Not free, but not too expensive: $50 for "developed markets" and $20 for "emerging markets", based on your login IP; you can take them 5 times within 1 year.
At the moment they only have 2 exams for the MASE level, but I'd guess if you ace your MASE practice, chances are you'll manage your real ASE exam just fine.
The official HP page is: http://h10120.www1.hp.com/certification/practice_exams.html
