Hi,
I am not quite sure if that fits here, but i would like to know what you think is the maximum length for a cable between the Port on the board and the sensor.. or for a shield...
That really depends on the sensor's impedeance and operating voltage. Can you provide a link for the sensor? There are various ways to extend cable length using driver components and such, but it really depends on the specifics of the device.
Lefty
Well, for one it would be interestering to know the max for the LCD Shield. It may sound ridicolous.. but is there any chance to get a connection over a distance of 30m - and no Xbee solution is available?
That is pretty long distance to send TTL signals, especially if the display data rate frequency is significant. It is certainly possible to do if you used driver/receiver chips such as used in RS-422 type communications applications which can send and receive TTL signals through thousands of feet of twisted pair cables.
http://datasheets.maxim-ic.com/en/ds/MAX1487-MAX491.pdf
Lefty
RS-485 will work up to 4000 feet or about 1200m
But you need your LCD driver board and the LCD to be in close proximity
PC <======= RS-485 4000ft or 1200m ===========> Arduino_WITH_LCD
RS-422 will also work up to 4000ft or 1200m
At the maximum distance your data rate will be seriously limited, you can only do about 100kbit/sec max at 4000ft
well, data rate is quite irrelevant as i only want to have some letters (2x16 max) per 30 seconds regularly - plus an irregular impulses from the lcd back to the arduino - but nothing more than a pressed button... The best thing would surely be a connection that would not neccessarily connect arduino and lcd shield in one place but like a cable between the two elements..
If you need to be able to separate the arduino and the LCD by 30meters ( 98ft ) then you have to use a serial backpack for the LCD and then run a serial link from the LCD to the arduino
You can use the wulfden LCD backpack http://wulfden.org/TheShoppe/k107/k107.shtml
Or the sparkfun LCD backpack SparkFun Serial Enabled LCD Backpack - LCD-00258 - SparkFun Electronics
Or the modern device LCD backpack Displays – Modern Device
thank you :0)
jm4648 on ebay also has an ATMEL based LCD backpack which is similar to the ones listed above and a little cheaper ( $9.99 instead of $14.99 or higher )
http://www.mardocks.com/LCD%20Controller/manual/manual%20rev%201a.pdf
http://search.ebay.com/_W0QQsassZjm4648
Seems to be on vacation right now though
Good luck 
Thanks for that kind help again :0)
Yet it was more a 'would like to know' question for the next time since i would not have a chance of testing what i had in mind anyway till august or so.. yet it is good to know that such stuff is possible.
thanks again :0)