here's the info on the iPod for yah:
The official BMW iPod connector is pretty good. I have one fitted and one spare (yours for £150

).
It works in place of your CD Changer (just like the Denison and Intravee) and will charge your iPod (excluding 6th gen, or new iPhone - although you can get a
converter that WILL charge the newer stuff for about a fiver).
You create up to five playlists in iTunes (called BMW1 to BMW5) and these correspond to the first five "disc" buttons along the bottom of the stereo. the sixth button cannot be assigned a playlist, but instead can be used to play all the tracks on the iPod.
The iPod connector works perfectly with the MFSW controls.
The connector end is simply an iPod cable that can be placed anywhere within the car. The official installation instructions recommend the glovebox, but I have mine in the little tray at the back of the central arm rest.
The Denison and Intravee appear to be the crowd favourites, and there are loads of posts on here about them.
I've not got any experience with any of these, but there are plenty of people here that rave about them
As mentioned, with ANY of the above three options, you WILL loose the use of the CD Changer if you have one (there IS a way to avoid this, but as I've only got the BMW iPod connector, I have only tested it with that... and it does involve a bit of electronics and soldering.. but still

)
If you want to keep your CD changer, then your next best bet is an AUX Cable.
There is an AMAZING (if I say so myself

) thread on how to create your own cable in less than an hour, for under a tenner.
You can find that thread using one of the links in my signature below.
There is also the "already built" option - the most expensive being the
BMW E85-specific AUX in retrofit. Which is £45 (which, for three bits of wire, a socket, two resistors, two capacitors and a bit of plastic is monumentally expensive imo!)
You can also use the
MINI R53 (£40.95) or
BMW E46 (£39.95) aux cables, but they are not quite plug and play (you need to jiggle the pins in the socket, but it's very simple and there are tonnes of guides on here for it).
You can also buy some 3rd party cables from the internet, with prices ranging from £10 to around £30... but make sure you search this forum first and find out which cable definately works - else you'll be pulling it apart and adding capacitors anyway (as in my aux thread

).
Personally, I have the BMW Ipod Connector AND the aux cable and can't see an advantage of switching to Denison or Intravee... installation appears to be much easier for the BMW specific iPod connector, and the only feature it DOESNT have is displaying track names on the radio headunit (which you can't read with the top down and the sun shining anyway

)
but that's just my own personal taste - I'm sure the three iPod-specific options all have different advantages and disadvantages depending on what it is you want for your money
Hope that helps!