I personally use and recommend all of the following Telephony tools...
Broadvoice
For my home phone and soft phone. $30 a month for free int'l calling.
eVoice
I've used this voicemail-to-email service for some clients PR lines.
Free Conference
For conference calls and recording interviews.
Grand Central
Another handy tool I use for voicemail with some clients PR lines.
Jajah
Handy when abroad for calling USA from my foreign cell phone.
Jangl
For widget based anonymous calling off blogs and profiles. (Full Disclosure: Jangl is a client of Courtland Brooks)
Send2Fax
Handy online fax service.
Simulscribe
Takes all my voicemails, transcribes them into emails. Huge time saver.
Skype
Backup for my Broadvoice line. Also for forwarding calls to whatever international cell phone I'm on, and for on the fly conference calls.
I'll add lists under categories for Web, Fun and Hardware that I use each Thursday for the next 3 weeks. Finance, Management and Telephony have been covered so far. Click on the 'Tips' category (see category cloud to the right) for future reference.
Please leave a comment if you have any additional telephony tools that you can recommend from personal experience.