PROBLEM I2C STELLARIS LM4F120 LaunchPad (Master) and LSM303 (Accelerometer Slave)

There are a couple of things I see here that will cause you problems. The first, and most obvious is the line:

HWREG(I2C0_MASTER_BASE + I2C_O_MCR) |= 0x01;

This puts the I2C controller into a test mode which loops transmitted data back to the receiver. You definitely want to remove this line.

Looking at the sensor spec you linked to, I also suspect that your I2C transaction code in bus() isn't correct. By using I2C_MASTER_CMD_SINGLE_SEND every time you want to send a byte, you send both a start and stop condition on every byte. The sensor datasheet, however, shows that the stop condition is only sent at the end of the whole transaction (as is normal for the I2C devices I've used). To control the placement of start and stop conditions when you are performing a multi-byte transaction, you should use I2C_MASTER_CMD_BURST_SEND_START one the first transaction (when you send the slave address), I2C_MASTER_CMD_BURST_SEND_CONT for each following byte you transmit then I2C_MASTER_CMD_BURST_SEND_FINISH on sending the final byte. You also need to make sure you call I2CMasterControl() once for every byte you want to read or write (I see at least one case above where you write 2 bytes between calls to the function). Note that the slave address is automatically sent when you send a start condition so the first call to I2CMasterControl() will send both the address byte and the first data byte.

Here's what I think you want to read a single byte from the sensor (though, please note that I've not used this device and have not compiled this code!):

tBoolean ReadSensorRegister(unsigned char slaveAddress, unsigned char Reg_Addr,
                            unsigned char *pucData)
{
    // 
    // Tell the master module what address it will place on the bus when
    // communicating with the slave. 
    //
    I2CMasterSlaveAddrSet(I2C0_MASTER_BASE, slaveAddress, false);

    //
    // Write the register addresss byte to the sensor.
    //
    I2CMasterDataPut(I2C0_MASTER_BASE, Reg_Addr);

    //
    // Send a start condition, slave address and first byte.
    //
    I2CMasterControl(I2C0_MASTER_BASE, I2C_MASTER_CMD_BURST_SEND_START);

    //
    // Wait until the current byte has been transferred.
    //
    while(I2CMasterIntStatus(I2C0_MASTER_BASE, false) == 0)
    {
    }

    //
    // Check for errors and abort if one occurred.
    //
    if(I2CMasterErr(I2C0_MASTER_BASE) != I2C_MASTER_ERR_NONE)
    {
        I2CMasterIntClear(I2C0_MASTER_BASE);
        return(false);
    }

    //
    // Set the slave address but this time we will be reading from the device.
    //
    I2CMasterSlaveAddrSet(I2C0_MASTER_BASE, slaveAddress, true);

    //
    // Send the adderss again with a (repeated) start condition. Read one
    // byte then send a stop condition.
    //
    I2CMasterControl(I2C0_MASTER_BASE, I2C_MASTER_CMD_SINGLE_RECEIVE);

    //
    // Wait until the current byte has been transferred.
    //
    while(I2CMasterIntStatus(I2C0_MASTER_BASE, false) == 0)
    {
    }

    //
    // Check for errors and abort if one occurred.
    //
    if(I2CMasterErr(I2C0_MASTER_BASE) != I2C_MASTER_ERR_NONE)
    {
        I2CMasterIntClear(I2C0_MASTER_BASE);
        return(false);
    }

    //
    // Read the value received.
    //
    *pucData = I2CMasterDataGet(I2C0_MASTER_BASE);

    //
    // All is well.
    //
    return(true);
}