You are in luck, because I have become an expert in the vibrating Accord phenominon. My 93' shook so bad, it was like getting a massage at every red light. The problem lies in the rear motor mount. It is, for some reason, vacuum controlled. The motor mount is fed vaccuum by a small solinoid mounted in the center of the firewall. When the car reaches idle, it electronically engages, passing vacuum to the mount. When the mount receives vacuum, it dampens the vibration. You have 3 possibilities.

1) The solinoid is bad. At idle, check the hose going down to the mount and confirm you have vacuum. Be careful not to break off the solinoid nipple cause you will have to replace the unit at a cost of $65. It might even be better to cut the hose and use a hose connector to re-attach.

2) The motor mount has gone bad. Replacement is a major nightmare and will take 3-4 hours. The new mount is $160 from Autozone.

3) The vacuum module mounted to the motor mount has a linkage arm that activates the mount. The arm will sometimes slip off the motor mount causing it to quit working. This is also a major nightmare, because most of the motor mount and the vacuum linkage arm are not accessible without, at least, removing the bolts from the mount so you can tip it over to gain access to the linkage. This was the problem with my car and, despite 3-4 hours work, turned out well because I did not need the $160 replacement.

If your Accord is vibrating at idle (worse when in gear (auto) or when the A/C is running, I guarantee this is your problem.