PLASTERPYRUS  I gave this thing a try and I said its OK, even kind of fun for awhile. Then it started to anoy me after awhile, so I turned it off and kinda forgot about it. Well I recently came across it again and I said to myself I'll give it a whirl, so I went to the developers sight to see how much it cost. Well this guy must be kidding! 20.00 dollars for this, sheez louis! Made me think how much I appreciate developers that give their time and know how, to give us (the mac community ) those real gems for free ( or donnations )!  
(Version 3.9)

PALADINO  Yeah, €15(about $20, currently) for this is HORRIBLY overpriced(I think ALL this developer's software is horribly overpriced).....but "Keyclick" works beautifully and is only $2.50.  
(Version 3.6)

PENGUIRL  Keyclick: $2.50; 0.30% CPU while in use.

Typewriter Keyboard: €15 (about $18); 8.20% CPU when IDLE!

'nuff said.  
(Version 3.4)

HENRIKTEKNIK  Also check Keyclick: http://www.macupdate.com/info.php/id/24053

Keyclick does the same, except for letting you choose custom sounds from the interface (although you can do it manually via 'Show Package Contents' in Keyclick's prefpane and replacing the sounds within).

15 euros for Typewriter Keyboard...

...$2.50 for Keyclick (that'd be approx. 1.90 euro)

The rest is your choice.  
(Version 3.4)

ORION MK. V  Works well, but too pricey for a one trick pony. About $10 is fair for something like this.  
(Version 3.2)

10CH  I downloaded this program and then saw in the comments that Mac has a similar option pre-installed by turning on certain things in the Sound/Universal Access system preferences.

I decided to try this program anyway, after using the Apple solution for a day.

Typewriter Keyboard is remarkably better... first because you don't have to live with a slow keystroke repeat, which honestly drove me crazy. And second because you can turn off sounds for certain keys (like shift, command, ctrl, option, esc...) and you can play different sounds for different keys (like delete, space, enter). It really is a completely different kind of solution than the Apple one (and much preferred if you ask me).

So, since it's free to tryout, I would definitely give both solutions a go. You might be annoyed by typing sounds on a keyboard and it's not worth the $15 bucks (honestly I'm not sure after only two days if I'll purchase the program), but to say you get the same experience from both solutions is a falsity.  
(Version 2.10)

ANONYMOUS  I have been searching for an app like this for a year or more. Aural feedback when a key makes contact allows me to type faster. Unfortunately, the one that comes with the Mac OS slows everything down and is not practical for speed typing. TK 2.7 has its own problems. First, although you can change the sounds for each key, there appears to be no way to SAVE the sound key mappings so that they autoload next time you start the programs. Second, I agree that $15 is absurd. There are a bazillion tiny interface improvements, such as this one, and at $15 each we will soon spend double the cost of the OS.

My solution? Spend $80 for a keyboard with both tactile and aural feedback. We'll see how it works.  
(Version 2.7)

SOFAMYSTIC  the typewriter sound as you press keys is built into panther. got his hint from macosxhints and it works great...

"In System Preferences, click Sound and turn on "Play user interface sound effects." Then switch to the Universal Access pane.

In the Keyboard tab, turn on Slow Keys, and move its Acceptance delay slider all the way to the right (Short). Confirm that "Use key click sounds" is turned on. Click Show All to activate the changes.

Now start typing and enjoy this sonic blast from the past. (Much to your chagrin, there's enough of a delay to drive you crazy, if you're a reasonably fast typist.)"- from mac osxhints website.  
(Version 2.7)

LETTERPRESS LOUIE  Built on the back of the famous TappyType.

Slicker interface. But unlike TT - which

was freeware - you can't apply TK to certain applications only without repeatedly opening and closing it. Seems to me that this is overpriced. Nice icon, though.  
(Version 2.6)

SCOTT DUTTON  While it may or may not be a bit overpriced, it was worth it to me, and I gladly paid the fee.

I don't miss the mechanical issues of a typewriter, but the sounds are part of the writing process for me and it's great to hear the clack and ding once again. It's perfect on my iBook.

Thanks for the fun.  
(Version 2.4)