One of my favorite voip brands has turned out be Linksys (now under Cisco). First small PBX I used was the LVS9000. It didn't turn out to be a great PBX but a lot of the associated products turned out very well.
The SPA942 is great general purpose phone. Can be used with many SIP phone systems including Asterisk. Also great for companies offering hosted PBX services.
The SPA962 with sidecar - great receptionist phone. The sidecar buttons can be configured for BLF, speed dial, and call pickup.
The SPA400 turned out be a very reliable 4 port analog gateway - although not advertised to work with Asterisk.
The PAP2T ATA's are great quality when used with a good analog phone - try the Aastra 9116 - MWI indicating light works, call waiting, hook flash, transfer button, and speaker phone.
The SPA8000 & SPA8800 are also great new products under the Small Business Pro line up.
And the legendary SPA3000 and SPA3101. Great combination of FXO,FXS, and router (SPA3102)
The SPA3000 lets you test a variety of PSTN / VOIP setups - truly one of the best hack devices!