To avoid a collection of stale issues on which additional vocabularies we might add to the crosswalk, I'll try and aggregate a running list into the thread here. At this time we don't have developer capacity to add crosswalks ourselves but PRs always welcome.

• code.gov (Crosswalk to US code.gov metadata schema #159)
• .ABOUT (was .ABOUT files exported in libraries.io #152)
• ADMS.SW (Should we crosswalk to ADMS.SW? #41)
• seon (From SWH archive- questions about DOAP, SEON, debtags, ADMS.SW, Wikidata, generators and statistics.. #127)
• debtags (From SWH archive- questions about DOAP, SEON, debtags, ADMS.SW, Wikidata, generators and statistics.. #127)
• jats (How do we link to JATS? Should it be added to the crosswalk? #48)
• bibtex (add mapping to bibtex software entries #58)
• DCAT (Should we review DCAT from W3C? #44)
• DIRT (Consider crosswalk to DIRT #119)
• DOECODE (See how DOE Code might benefit from Codemeta #121)
• package purls (Consider purl Package URLs #175)
• SWORD / AtomPub (Crosswalk AtomPub and how to use codemeta with SWORD [crosswalk]  #163)
• COIN-OR (add COmputational INfrastructure for Operations Research to crosswalk #77)
• Research-object specs (Research Object specs #46)
• ....

Arguably not all of these should be crosswalked, in some cases something more machine-readable such as an ontology specification could provide a more practical mechanism.