<select id="redirect" onchange="location.href=this.value;">
<option value="" selected disabled>Select report!</option>
<option value="AttendanceReports.aspx">Attendance Report</option>
<option value="ExamReports.aspx">Exam Report</option>
<option value="OtherReports.aspx">Other Reports</option>
</select>
But this is pure client side, if you need some other action on server side too, you can use that approach also, see:
http://msdn.microsoft.com/en-us/library/540y83hx(v=vs.100).aspx[
^]