A friend of mine just got himself the powerful Snom VOIP phone that boots Linux.

German Snom Technology AG introduced the Snom 220 professional VOIP phone in August. The VOIP phone runs embedded Linux and is configured via a web interface. The phone features a 128 x 64 pixel graphical backlit display. Up to three Keypad units (photo shows one attached) can be attached to the phone increasing the number of programmable keys up to 60. Features include UPnP, STUN, ENUM and an extra Ethernet port.
More details on Snom 220 product page. The Snom 220 sells for 319 Euros on their Shop.

Snom 220 VOIP Phone Features:
Features

• graphical backlit display (128x64)
• 5 programmable function keys
• RFC 3261-compliant SIP stack
• H.323/H.450 stack
• NAT support
• 16-bit, 16 kHz audio subsystem
• 2 port Ethernet switch
• national language support (NLS)
• Asian Language Support (ALS): Japanese
• loose routing and strict routing support
• blind and attended transfer
• call hold, call wait
• music on hold support
• call completion
• call intrusion
• call divert
• number guessing
• speed dialing
• handsfree mode dialing
• missed calls, taken calls
• call waiting indication
• STUN client (NAT traversal)
• Plug and Play support (UPnP)
• HTTP Server
• phone book
• conference call
• redial
• several ring tones
• DTMF


About Snom:
snom technology AG was founded in 1996 in Berlin. It offers products and services in the voice-over-IP (VoIP) area, speech communication over networks. So far the main users have been small and medium-sized companies as well as Internet Service Providers. snom specializes in manufacturing Linux-based VoIP telephones, based on open standards and SIP. snom is a customer-oriented company producing state-of-the-art, affordable VoIP phones with a high cost-performance ratio and a range of practical SIP applications for business. With software services and the SIP Provider Partnership Program, snom is strengthening its position as a full-service company for SIP.