Most bonuses are not really aimed at the low stakes players - they're just not the players rooms want to attract. I reckon this is a big mistake on the part of the poker rooms and they should make the bonuses easier to clear as every high stakes player was low stakes to begin with.
The
pokerstars bonus is quite good (although low) because it gives you 6 months to clear the points requirement whereas alot of rooms only give you 30 days or so, which is too fast for most new players.
I won't mention any names but there are some sites out there advertising out of date or 'fantasy' bonuses (fantasy as in they don't actually exist but once you've signed up at a room it's too late to change your bonus). Choose your bonus from a reputable website and they will give you all the info you need about redeeming the bonus (if they don't give full info - don't sign up with that code). Also, try the email test (perhaps set up a new free email account to avoid the masses of spam you may receive from 'naughty' websites) - email the website with a question - if they don't get back to you within a reasonable amount of time (say 24 hours - allowing for time differences) then forget it and move onto somewhere where they value you and will answer honestly any questions you have.
Most of the sites (including mine) that advertise here are pretty straightforward and can be trusted to have 'reliable' bonuses.