http://wiki.kolmisoft.com/index.php/Asterisk_Background_performance_test performance tests for asterisk on 4 Intel Cores @ 2GHz, 2 GB RAM, over sip, recorded media playback – results: saturates 100mb network at ~1000 simultaneous calls, one way GSM playback.
http://wapo-spb.livejournal.com/3912.html asterisk stress testing (Livejournal post in russian )
http://www.cisco.com/en/US/prod/collateral/voicesw/ps6788/vcallcon/ps7194/product_data_sheet0900aecd805c3cc1.pdf Cisco Service Node for Linksys One – integrated solution for linksys voip CPE (registration, services, provisioning), consists of cisco network gear (chassis + console server ) , 2 HP DL G380G4 servers + MSA100 storage / FreeBSD, PostgreSQL, OpenSER, NET-SNMP, DIND DNL (Dynamically-Loadable Zone)
http://habrahabr.ru/blogs/development/111161/#habracut Review for open source and commercial echo canceling libraries
http://downloads.polycom.com/voice/voip/sip_sw_releases_matrix.html SIP Firmware for Polycom SoundPoint IP Phones and conf. devices
http://www.slideshare.net/twilio/reinventing-the-dialplan-slides-from-twilios-astricon-2009-talk Company provides Virtual PBX - asterisk “in the cloud”, with HTTP/XML/REST API (business-level google voice)
http://www.skype.com/intl/en/business/products/pbx-systems/asterisk/ “channel skype” asterisk module, allows you to connect your asterisk box to skype
http://news.slashdot.org/comments.pl?sid=1157677&cid=27162671 well, this is from slashdot: informative but not confirmed
http://www.simionovich.com/ useful blog about voip tech and asterisk
http://code.google.com/p/red5phone/ untested. just something to watch for.