Something new is on the way: FlexibleShare
Flex based version of Alfresco Share / Flex based Portal Container (Open Source)
1. Dashboard dashlet/portlet drag /drop in Flex
2. Portlets in Flex and HTML/Ajax
3. Leverages FlexSpaces components
4. Leverages Alfresco Share (site model, rest apis, surf, dashlets),
5. Additonal Flex components for wikis, blogs, discussions, calendar
6. Leverage Liferay, (supports jsr-168, wsrp) in a later stage
7. Reporting/BI (JasperReports, Pentaho, BIRT)
8. BPM (JBoss jBPM in Alfresco)
9. Desktop drag/drop of files with AIR
Note on the name: Alfresco Share and Surf are already “flexible” (in the able to adapt to new situations sense). Also you can implement Share/Surf components/dashlets with Flex (as I did with the FlexSpaces page site components). The difference with FlexibleShare is that the container itself is in Flex and the primary way for implementing dashlet/portlet UI is Flex (and Flex+AIR). Surf dashlets and Liferay portlets in HTML/Ajax are still supported.
Other things: the use of a web-tier Flex compiler (like the Flex plugin for Grails does) could be used to allow Flex forms/UI to be added (and compiled automatically) without having to use a development tool. BlazeDS support like in this plugin would also be nice too for higher performance data transfer.
Update: See description of FlexibleShare prototyping mentioned in my Genesis / Flex Portals / Open Source blog post.