hello
A few months a go i've bought an Arduino starters kit.
I want to buy more stuff for my arduino.
What must i buy and can i use for a lot of projects?
I've now an arduino uno should i buy a mega?
My buget is 150 euro ($200).
Thanx
duix
Think of what you want to do. You can go software or hardware. Have a look on ebay at the things available. Some from UK and some from China. Getting hold of a second hand scope might be a good idea, I was given one recently. There is a lot of old equipment in lofts that is very useful. The main thing to do is to work out what you want to do and then ask how to do it. You could make your own Arduino for instance on veroboard. You can buy a 328 chip with bootloader, socket , crystal and capacitors for under £4 from Uk source on Ebay. Then connect up using a breadboard or a soldering iron and some wire.
I dont know what comes in your starter kit (you didnt post a link)..
but this a fun little kti to have for quickly prototyping stuff:
I would also suggest a resistor kit & capacitor kit. (wide variety/range/values)
voltage regulators in various outputs (+1.8v, +3.3v, +5v, +6, +9v, +12v)
transistors
mosfets
various IC's for breadboarding/prototyping:
MAX7219/MAX7221
74HC595's
TLC5940's
WS801/03
LM3914N's
find a project that uses one of those chips and follow it.
for some other breakout boards, maybe:
SD card
Accelerometer
RF-ID reader/writer
BlueTooth
lots of jumper wire.
I also suggest following what was posted prior, about learning how to make barebones/basic Arduino compatible circuits..
I find/have found a lot of this stuff will 'pop-up' during your 'beginner adventures'....
or be used on many of the tutorials/articles you see when starting to play with this sorta stuff.. 
A kit of resistors in different values and a bag of 2N2222 transistors. That way if you blow a transistor you don't have to worry about it, only why it happened!
Thanx for the answers!
This is my starter kit:https://iprototype.nl/products/kits/iprototype-starterkit
What is the difference between the ic?
MAX7219/MAX7221
74HC595's
TLC5940's
WS801/03
LM3914N's
MAX7219/7221:
*Serially interfaced LED driver
*(supports up to 64 individual leds or 8 x 7-segment displays)
*matrix wiring/multiplexing/ 1 x resistor for all leds
*no pwm
http://datasheets.maximintegrated.com/en/ds/MAX7219-MAX7221.pdf
http://playground.arduino.cc/Main/MAX72XXHardware
74HC595:
*Shift register
*(referred to as the '595 chip sometimes around here)
*adds 8 more 'outputs' (only takes up 3 lines to use)
*support pwm
http://forum.arduino.cc/index.php/topic,39818.0.html
http://code.google.com/p/shiftpwm/
https://www.google.com/search?q=Arduino+%2B+74HC595&tbm=isch&tbo=u&source=univ&sa=X&ei=3XPAUYvEFcWs4AOW_4HgBQ&ved=0CDoQsAQ&biw=1173&bih=742
TLC5940:
*16 channel PWM
*handy for expanding the number of PWM outputs
*When using with RGB LEDs get LEDs with common anode
http://playground.arduino.cc/learning/TLC5940
http://code.google.com/p/tlc5940arduino/
http://forum.arduino.cc/index.php/topic,17339.0.html
LM3914:
*Dot/Bar Display Driver
*you can use a supply voltage between 3 and 25V DC
*each LED can draw up to 10mA
*10 x leds
http://tronixstuff.wordpress.com/2010/04/07/part-review-the-lm3914-dotbar-display-driver/
http://www.electroschematics.com/6390/lm3914-datasheet/
https://www.google.com/search?q=Arduino+%2B+LM3914N&tbm=isch&tbo=u&source=univ&sa=X&ei=LnrAUciOCrfK4AO5yIHoCg&ved=0CEAQsAQ&biw=1173&bih=718