Ask HN: Marketplaces for mashing business apps?

Other than Salesforce.com's AppExchange, are any business-oriented software marketplaces for add-ons getting traction?

I've looked into WebEx Connect Marketplace (vaporware?) and Google Solution Marketplace (anyone else heard of it?), but other than AppExchange I can't see anyone making much of a go of it (yet).

I expect that more AppExchange-like marketplaces to emerge to provide a more cohesive experience as Enterprise shifts out from corporate hardware to cloud/Saas-based platforms, but am not seeing much action just yet.

Has anyone got a clear fix on emerging contenders?