Steve Hays wrote a post about the distinction between viewing the eucharist as a sign and viewing it as a sacrament.
Here's an article he wrote about the lack of Biblical evidence for the Roman Catholic view of the eucharist.
Gene Bridges addresses the Lutheran view of communion here. Steve has written some posts on the subject as well, like here and here.
He's also written about some problems with belief in a physical eucharistic presence here and here.
Here's an index of material Rhology and others have written regarding the relationship between a eucharistic presence and Monophysitism.
Here's a post Steve wrote that applies Catholic reasoning about the eucharist to other Biblical contexts.
Concerning John 6, see here, here, here, and here. And here's a post in which Steve discusses John 6 and the Passover meal.
Steve addressed Paul's comments on the eucharist in 1 Corinthians 11. See, also, here.
This article addresses a common misrepresentation of what Ignatius wrote about the eucharist. The post and the comments section that follows also address the eucharistic beliefs of other historical sources, like Augustine.
I wrote about some neglected patristic evidence against a physical presence in the eucharist here.
Here's a thread that, in part, discusses the inconsistency between Irenaeus' view of the eucharist and the Catholic view. In the comments section that follows, Steve and I discussed some eucharistic issues with a Catholic priest.
Gene wrote a post that's partially about paedocommunion. And here's a thread about paedocommunion and pregnancy.
Steve wrote an article about some similarities between communion and Christian burial.
Here's a post by Jus Divinum that's partly about how Reformed Baptists view the eucharist.
Gene wrote a post that's partly about how communion should be implemented in the church, such as whether unbaptized individuals should be permitted to participate.