The new school comparison tool on the Department for Education's website
is a pretty useful tool; it gives parents a chance to easily compare schools in a variety of ways. You can compare results, spend-per-pupil, Ofsted reports and so forth.
One thing it most obviously illustrates is that there is no spending data for academies -- and presumably won't be for free schools too. I think the "spend-per-pupil information" section is very useful because you can see how much schools are spending on their teaching staff, supply staff, catering and so on and compare with other schools who've released this data. I am all for parents asking schools about this issue; if it's obvious that a school is spending comparatively little on teaching staff compared with administration then perhaps questions need to be asked. But clearly this can't be done in the case of academies.