Actually the Alesis Q88 gets good reviews on Amazon.
http://www.amazon.com/Alesis-Q88-88-Key-Keyboard-Controller/dp/B00BSXJY64
Inexpensive MIDI controller with a true MIDI out port as well as USB with semi-weighted keys that have very good reviews.
As previously stated, you'll either have to use this with your computer acting as the synthesizer using VSTi Virtual Soft Synth Instruments or else pick up a used rack module like a Motif XS Rack or Korg Triton or TR Rack and an amp from craigslist or ebay and use that to generate your sounds.
As for a starter keyboard, this seems to be very inexpensive and very well thought of by its users and if you plan to learn to play with a true piano style then 88 weighted keys is the way to go.
The nicest thing about a MIDI controller as opposed to a synth keyboard is that you'll never outgrow it. If you need more or better sounds just add a new module or soft synth and it will keep on going til it finally dies of old age.
No disrespect to Mike, but if you are starting out with keyboards then this is the way to go instead of dropping a few hundred quid on a low end compromise keyboard that you will either end up selling again in a few years or else find too difficult and give up on entirely after a few months.
The Q88 seems reasonably priced and well worth the money for a beginner or a pro alike.
Gary