Well i was experimenting a bit with usb devices on the wii, but my code returns that there are zero devices present, despite the fact that my external hard drive is powered and connected and my usb microphone is connected. Am i doing anything wrong?

My code:

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 

#define DEVLIST_MAXSIZE	8

static u32 *xfb;
static GXRModeObj *rmode;


void Initialise() {
	VIDEO_Init();
	WPAD_Init();
 
	rmode = VIDEO_GetPreferredMode(NULL);

	xfb = MEM_K0_TO_K1(SYS_AllocateFramebuffer(rmode));
	console_init(xfb,20,20,rmode->fbWidth,rmode->xfbHeight,rmode->fbWidth*VI_DISPLAY_PIX_SZ);
 
	VIDEO_Configure(rmode);
	VIDEO_SetNextFramebuffer(xfb);
	VIDEO_SetBlack(FALSE);
	VIDEO_Flush();
	VIDEO_WaitVSync();
	if(rmode->viTVMode&VI_NON_INTERLACE) VIDEO_WaitVSync();
}

void waitForButtonDown(int button){
	u16 buttonsDown;
	do {
		WPAD_ScanPads();
		buttonsDown = WPAD_ButtonsDown(0);
	} while(!(buttonsDown & button));
	printf("Button pressed\n");
}

int main() {
 
	Initialise();
	
	s32 test = USB_Initialize();
	printf("USB has been initialized: %d\n", test);
	printf("Press A to continue...\n\n");
	waitForButtonDown(WPAD_BUTTON_A);
	
	u8 n;
	u8* buffer;
	buffer = memalign(32, DEVLIST_MAXSIZE << 3);
	memset(buffer, 0, DEVLIST_MAXSIZE << 3);
	printf("DEVLIST_MAXSIZE: %x\n", (DEVLIST_MAXSIZE << 3));
	if(buffer != NULL){
		test = USB_GetDeviceList("/dev/usb/oh0",buffer,DEVLIST_MAXSIZE, 0, &n);
		printf("Getting usb device list: %d\n", test);
		printf("Found %d devices!\n",n);
	}
	else
		printf("Error: buffer is null.\n");
	printf("Press A to continue...\n\n");
	waitForButtonDown(WPAD_BUTTON_A);
	
	test = USB_Deinitialize();
	printf("USB has been deinitialized: %d\n", test);
	printf("Press B to continue...\n");
	waitForButtonDown(WPAD_BUTTON_B);
 
	printf("Exiting...\n");
	return 0;
}

For my usb related code i looked at this example

That's old code. There's at least one major bug with it, IOS expects MEM2 for USB stuff. So this is no good:
buffer = memalign(32, DEVLIST_MAXSIZE << 3);

You should take a look at usbstorage.c (and other usb code) in devkitpro svn, but one way is:

static s32 hId = -1;
buffer = iosAlloc(hId, DEVLIST_MAXSIZE << 3);

Also keep in mind that not all usb devices are detected. You can take a look at the usb2 support cios (202) and code for that, but it's still experimental.