upload.m

NSString *urlString = @"http://yourserver.com/upload_huge_file";
NSString *filename = @"filename";
NSString * pathToHugeFileToPost = @"hugeFile";

NSMutableURLRequest * request= [[[NSMutableURLRequest alloc] init] autorelease];
[request setURL:[NSURL URLWithString:urlString]];
[request setHTTPMethod:@"POST"];

NSString *boundary = @"---------------------------14737809831466499882746641449";
NSString *contentType = [NSString stringWithFormat:@"multipart/form-data; boundary=%@",boundary];

[request addValue:contentType forHTTPHeaderField: @"Content-Type"];

NSString * tempFile =	[NSTemporaryDirectory() stringByAppendingPathComponent: [NSString stringWithFormat: @"%.0f.%@", [NSDate timeIntervalSinceReferenceDate] * 1000.0, @".data"]];
if(![[NSFileManager defaultManager] fileExistsAtPath: tempFile]) {
	[[NSFileManager defaultManager] createFileAtPath: tempFile contents:nil attributes:nil];
}
NSFileHandle *handle = [NSFileHandle fileHandleForWritingAtPath: tempFile];


[handle writeData:[[NSString stringWithFormat:@"\r\n--%@\r\n",boundary] dataUsingEncoding:NSUTF8StringEncoding]];
[handle writeData:[[NSString stringWithFormat:@"Content-Disposition: form-data; name=\"userfile\"; filename=\"%@.jpg\"\r\n", filename] dataUsingEncoding:NSUTF8StringEncoding]];
[handle writeData:[[NSString stringWithString:@"Content-Type: application/octet-stream\r\n\r\n"] dataUsingEncoding:NSUTF8StringEncoding]];

//This will use very little memory as it writes the new file out to disk.
[handle writeData:[NSData dataWithContentsOfMappedFile:pathToHugeFileToPost]];

[handle writeData:[[NSString stringWithFormat:@"\r\n--%@--\r\n",boundary] dataUsingEncoding:NSUTF8StringEncoding]];

[handle synchronizeFile];
[handle closeFile];

//assign body to another memory mapped file
NSData * postBody = [NSData dataWithContentsOfMappedFile:tempFile];
[request setHTTPBody:postBody];

NSData *returnData = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil];
NSString * returnString = [[NSString alloc] initWithData:returnData encoding:NSUTF8StringEncoding];
NSLog(@"%@",returnString);