- (BOOL)connectionPOST:(NSURLRequest *)aRequest 
             withParams:(NSDictionary *)aDictionary {
    
  if ([aDictionary count] > 0) {
    NSMutableURLRequest *request = [[NSMutableURLRequest alloc] 
                                      initWithURL:[aRequest URL]];
    [request setHTTPMethod:@"POST"];
        
    NSMutableString *postString = [[NSMutableString alloc] init];
    NSArray *allKeys = [aDictionary allKeys];
    for (int i = 0; i < [allKeys count]; i++) {
      NSString *key = [allKeys objectAtIndex:i];
      NSString *value = [aDictionary objectForKey:key];
      [postString appendFormat:( (i == 0) ? @"%@=%@" : @"&%@=%@" ), key, value];
    }
        
    [request setHTTPBody:[postString dataUsingEncoding:NSUTF8StringEncoding]];
        
    [NSURLConnection connectionWithRequest:request delegate:self];
        
    [postString release];
    postString = nil;
        
    [request release];
    request = nil;
        
    return YES;
  } else {
    return NO;
  }
}

// ---------------------------------------------
// usage

NSURL *url = [NSURL URLWithString:@"http://www.undolog.com"];
NSURLRequest *request = [NSURLRequest requestWithURL:url];

// Send name=Mark&lastname=Smith   
NSDictionary *params = [[NSDictionary alloc] 
                         initWithObjectsAndKeys:
                         @"Mark", @"name", 
                         @"Smith", @"lastname", nil];
[self connectionPOST:request withParams:params];
[params release];
params = nil;

http://www.undolog.com

Send POST parameters

Objective C