Recently Harmonix transitioned Rockband.com to Harmonixmusic.com and a few things were lonst along the way including the ability to link your Rock Band 3 band with Rockband.com. This renders the "Well Connected" achievement discontinued. This now leaves Rock Band 3 with one discontinued achievement and one partially discontinued achievement.
All items from the Monsters Love Candy store have now been pulled causing the "Rainbow Eyes" achievement to now become discontinued. There has been no announcement from the developer regarding the items being pulled from the store, so there is a possibility that they could come back, however, I wouldn't hold my breath. This now leaves Monsters Love Candy with two discontinued achievements.
Ubisoft announced today that servers will be closing for a number of their games on August 8, 2014, however, this will not discontinue achievements in all of the games. Below is the complete list of games with some kind of online functionality going down. Following the title is the number of discontinued achievements prior to the shutdown in parentheses and the number of achievements affected by the shutdown in brackets. An asterisk indicates that it was possible to earn the achievement online but is also possible to earn the achievement in either offline game modes such as single player or system link. These numbers are based on flags from Trueachievements.com and my knowledge of these games. The post from Ubisoft is available here.
- America's Army True Soldiers - (1), 
- Avatar, James Cameron's - (0), 
- EndWar, Tom Clancy's - (20 + 1 unobtainable), [25*]
- Ghost Recon Advanced Warfighter 2, Tom Clancy's - (0), [39*]
- Motionsports Adrenaline - (0), 
- PowerUp Heroes - (0), [8*, 1]
- Shaun White Snowboarding - (0), [?] I don't know enough about this game to get an accurate number. It appears that some will be affected.
- Splinter Cell Double Agent, Tom Clancy's - (0), [17*]
I am not going to go into detail on each individual game except for Motionsports. Unless you have challenges in progress it will not be possible to earn the online required, challenge related achievements because they take a week to finish.