Lets start with Portals space:

ATG:
Art Technology Group – A group who created art for Internet world by providing common face to all the applications within the organization/

BroadVision:
Broad-vision = enterprise wide vision? Nicely framed but their vision is really going hey-ward

Vignette:
A decorative design or small illustration used on the title page of a book or at the beginning or end of a chapter. A decorative design for your information capturing from beginning to end, from all systems across the organization.

JBoss Portal:
Java Boss?

Liferay Portal:
Life – ray : a ray of life for all the vendors who can not afford commercial portal products.

Plone:
Anyone out there help me. I have no clue about it

ECM/DM/WCM Space:

Documentum:
Document -um means documents – used as an expression of doubt, hesitation, deliberation, interest, etc. Confused about managing your documents? Here we are at your service Very Nice !

FileNet:
Files over Net? Well makes sense based on the offerings that they have. Good job !!!

Alfresco:
Out-of-doors; in the open air. It does express its open source nature but no hint about ECM? What if tomorrow its acquired by some big ECM giant?

HummingBird:
Any bird of the family Trochilid, which include around four hundred species. Well a good way to express that it can handle any content type.

Interwoven:
To weave together, as threads, strands, branches, or roots. Nice way to express the product

Fatwire:
Thick wire? A thick wire that is bringing all the content contributors together under one system

Looking forward for comments about the existing products and for including new products in the list

Day Launches JSR-170 CMS Repository Connectors