NumberGarage allow you to park or forward your number and take control of your number such as reserving the number for future use such as changing carrier, or  forward your cell  number to landline or vice versa and lots more and it also allow you to use Google Voice. The Sign up process is relatively very simple and currently is only available in the US.
Have a look and tell me what you think?

 
TwitterFone is free service that lets you update your Twitter feed using your voice from any mobile or cell phone. Simply you call a local number,  speak your tweet, and hang up. A short while later, your tweet will be posted on Twitter.
TwitterFone is great for when you’re on the go or without access to WiFi or Internet, Not only this You can also listen to your Twitter stream, and while you’re listening, you can record a reply or send a direct message.
In order to use TwitterFone you need to …

SlyDial allow you to call any US cell phones and go directly into it’s voicemail box without letting the user’s phone ringing. Its like calling the returning the call to the other persons’ call without actually talking to them.
SlyDial is simple to use simpley call SlyDial 2670SLYDIAL (267-759-3425) from any landline or mobile phone, listen to some ads, and then dial the number you want to call. There is also premium service available for $ 2.95 or $ 29.95 per year. This is ad-free service, allow you to save contacts, …

TBUZZ is your browser’s bookmarklet is an easy way to talk about the websites you visit on Twitter. TBUZZ makes it easy to tweet the page you’re visiting or keep track of the buzz around it.

OnTheRoad is a new web app developed by  Devmasters Inc from Czech Republic. The application will be presented at Mix’09. The application has lots of features such as sharing planning trip with schedules, pin-up on the map mesh, share and collabrate (and TripBook (a blog feature to write about your trips, articles, media comments etc). 
More info: OnTheRoad