The big problem with UITextView is there isn't any native way to hide the keyboard once the input ended.
The following code describes a DissmisableTextView. This view extends UITextView adding on top of the keyboard associated with this UITextView a toolbar with a "Done" Button :



Here is the code : 
//
//  DismissableTextView.h
//  
//  A textView allowing to dismiss keyboard with a toolbar and a
//  Done button on top of the keyboard
//
//  Created by Vincent Demay on 02/07/09.
//

#import 


@interface DismissableTextView : UITextView {

	UIToolbar* keyboardToolbar;
}

- (void) keyboardWillShow:(NSNotification *)note;
- (void) dismissKeyboard;

@end




//
//  DismissableTextView.m
//  murena
//
//  Created by Vincent Demay on 02/07/09.
//

#import "DismissableTextView.h"


@implementation DismissableTextView


- (id)initWithFrame:(CGRect)frame {
    if (self = [super initWithFrame:frame]) {
		//register a specific method on keyboard appearence
        [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardWillShow:) name:UIKeyboardWillShowNotification object:nil];
    }
    return self;
}



- (void)keyboardWillShow:(NSNotification *)notification 
{	
    for (UIWindow *keyboardWindow in [[UIApplication sharedApplication] windows]) {
		
        // Now iterating over each subview of the available windows
        for (UIView *keyboard in [keyboardWindow subviews]) {
			
            // Check to see if the description of the view we have referenced is UIKeyboard.
            // If so then we found the keyboard view that we were looking for.
            if([[keyboard description] hasPrefix:@"<UIKeyboard"] == YES) {
				NSValue *v = [[notification userInfo] valueForKey:UIKeyboardBoundsUserInfoKey];
				CGRect kbBounds = [v CGRectValue];
				
				if(keyboardToolbar == nil) {
					keyboardToolbar = [[UIToolbar alloc] initWithFrame:CGRectZero];
					keyboardToolbar.barStyle = UIBarStyleBlackTranslucent;
					
					UIBarButtonItem *barButtonItem = [[UIBarButtonItem alloc] initWithTitle:@"Done" style:UIBarButtonItemStyleBordered target:self action:@selector(dismissKeyboard)];
					UIBarButtonItem *flex = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemFlexibleSpace target:nil action:nil];
					NSArray *items = [[NSArray alloc] initWithObjects:flex, barButtonItem, nil];
					[keyboardToolbar setItems:items];	
					[items release];	
				}				
				
				[keyboardToolbar removeFromSuperview];
				keyboardToolbar.frame = CGRectMake(0, 0, kbBounds.size.width, 30);
				[keyboard addSubview:keyboardToolbar];
				keyboard.bounds = CGRectMake(kbBounds.origin.x, kbBounds.origin.y, kbBounds.size.width, kbBounds.size.height + 60);
				
				for(UIView* subKeyboard in [keyboard subviews]) {
					if([[subKeyboard description] hasPrefix:@"<UIKeyboardImpl"] == YES) {
						subKeyboard.bounds = CGRectMake(kbBounds.origin.x, kbBounds.origin.y - 30, kbBounds.size.width, kbBounds.size.height);	
					}						
				}
            }
        }
    }
}

- (void) dismissKeyboard {
	[self resignFirstResponder];
}



- (void)dealloc {
    [super dealloc];
}


@end