Disappointed by the lack of Evernote love for the iPhone SDK I decided to port their python example to Cocoa. This code snippet should work with Cocoa and Cocoa Touch.

#import "EvernoteBackup.h"

#import "THTTPClient.h"
#import "TBinaryProtocol.h"
#import "UserStore.h"
#import "NoteStore.h"

@implementation EvernoteBackup

- (void)Test
{
	NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
	// Keep this key private
	NSString *consumerKey = [[[NSString alloc] 
		initWithString: @"YOUR_CONSUMER_KEY_HERE" ] autorelease];
	NSString *consumerSecret = [[[NSString alloc] 
		initWithString: @"YOUR_CONSUMER_SECRET_HERE"] autorelease];
	// For testing we use the sandbox server.
	NSURL *userStoreUri = [[[NSURL alloc] 
		initWithString: @"https://sandbox.evernote.com/edam/user"] autorelease];
	NSString *noteStoreUriBase = [[[NSString alloc] 
		initWithString: @"http://sandbox.evernote.com/edam/note/"] autorelease];
	// These are for test purposes. At some point the user will provide his/her own.
	NSString *username = [[[NSString alloc] 
		initWithString: @"YOUR_USERNAME_HERE"] autorelease];
	NSString *password = [[[NSString alloc] 
		initWithString: @"YOUR_PASSWORD_HERE"] autorelease];

	THTTPClient *userStoreHttpClient = [[[THTTPClient alloc] 
		initWithURL:userStoreUri] autorelease];
	TBinaryProtocol *userStoreProtocol = [[[TBinaryProtocol alloc] 
		initWithTransport:userStoreHttpClient] autorelease];
	EDAMUserStoreClient *userStore = [[[EDAMUserStoreClient alloc] 
		initWithProtocol:userStoreProtocol] autorelease];
	EDAMNotebook* defaultNotebook = NULL;

	BOOL versionOk = [userStore checkVersion:@"Cocoa EDAMTest" :
						[EDAMUserStoreConstants EDAM_VERSION_MAJOR] :
						[EDAMUserStoreConstants EDAM_VERSION_MINOR]];

	if (versionOk == YES)
	{
		EDAMAuthenticationResult* authResult = 
			[userStore authenticate:username :password 
				:consumerKey :consumerSecret];
		EDAMUser *user = [authResult user];
		NSString *authToken = [authResult authenticationToken];
		NSLog(@"Authentication was successful for: %@", [user username]);
		NSLog(@"Authentication token: %@", authToken);

		NSURL *noteStoreUri =  [[[NSURL alloc] 
			initWithString:[NSString stringWithFormat:@"%@%@", 
				noteStoreUriBase, [user shardId]] ]autorelease];
		THTTPClient *noteStoreHttpClient = [[[THTTPClient alloc] 
			initWithURL:noteStoreUri] autorelease];
		TBinaryProtocol *noteStoreProtocol = [[[TBinaryProtocol alloc] 
			initWithTransport:noteStoreHttpClient] autorelease];
		EDAMNoteStoreClient *noteStore = [[[EDAMNoteStoreClient alloc] 
			initWithProtocol:noteStoreProtocol] autorelease];

		NSArray *notebooks = [[noteStore listNotebooks:authToken] autorelease];
		NSLog(@"Found %d notebooks", [notebooks count]);
		for (int i = 0; i < [notebooks count]; i++)
		{
			EDAMNotebook* notebook = (EDAMNotebook*)[notebooks objectAtIndex:i];
			if ([notebook defaultNotebook] == YES)
			{
				defaultNotebook = notebook;
			}
			NSLog(@" * %@", [notebook name]);
		}

		NSLog(@"Creating a new note in default notebook: %@", [defaultNotebook name]);

		// Skipping the image resource section...

		EDAMNote *note = [[[EDAMNote alloc] init] autorelease];
		[note setNotebookGuid:[defaultNotebook guid]];
		[note setTitle:@"Test note from Cocoa Test."];
		NSMutableString* contentString = [[[NSMutableString alloc] init] autorelease];
		[contentString setString:	@"<?xml version=\"1.0\" encoding=\"UTF-8\"?>"];
		[contentString appendString:@"<!DOCTYPE en-note SYSTEM \"http://xml.evernote.com/pub/enml.dtd\">"];
		[contentString appendString:@"			<en-note>Here is the Olive Tree Test note.<br/>"];
		[contentString appendString:@"			</en-note>"];		
		[note setContent:contentString];
		[note setCreated:(long long)[[NSDate date] timeIntervalSince1970] * 1000];
		EDAMNote *createdNote = [noteStore createNote:authToken :note];
		if (createdNote != NULL)
		{
			NSLog(@"Created note: %@", [createdNote title]);
		}
	}

	[pool drain];
}

@end

Again your mileage may vary but I think this gives you the gist of how to talk to the Evernote servers.