Here you will find some tips about programming an arduino. There are many sites which have good arduino tutorials  but most of them do not go into details of what i find the more difficult programming bits and pieces. Here you can find some of these. In addition you can find how to interface several different integrated circuits to the arduino. These mini projects include the hardware and software needed to make the project. So dont be shy and simply try it. They are really simple so anyone can make them. You will still get the kick from making them work. 🙂 There are several accelerometer and gyroscopes which i experimented with whilst making the segway clone, but also include some real time clocks, temperature sensors and magnetometer. There is even an article about how to interface the polar heart rate chest belt to an arduino. If you have any specific ideas of integrated circuits you would like interfaced to an arduino please let me know and i will see if i can make an arduino tutorial out of it.
Just click on the link below and you will be directed to the corresponding arduino tutorial.

SHT11          BMA180       ITG3200     HMC5843      RMCM01
ADXL335    IDG300         MMA7455   LIS302LD     DS1307
DS18B20     24C256          24C16           PCF8583       TSOP1838
CME6005    Max7456

Arduino tutorial Datasheets

If you are looking for the datasheets for these you can find them here.

SHT11        BMA180   ITG3200     HMC5843    RMCM01
ADXL335   ITG300    MMA7455   LIS302dl     DS1307
DS18S20    24C256     24C16           PCF8583     TSOP1838
CME6005   Max7456

Buy

There are very many sites selling arduino stuff. I use the following major sites because i trust them and they basically deliver good service.
mouser       digikey        farnell 

Tips:
Inverting a bit PortD=^bit4;