Here's IBM's answer to Pipes, Gears and the rest: DAMIA. It looks interesting in itself, and I liked to hear in an introductory video that they use the term "data mashup" to distinguish it from properly user-facing mashups, which might be built using the data produced by DAMIA. It takes the usual inputs - RSS, data as a spreadsheet - plus XML and, soon, database connections.
The other thing that is interesting about the phenomenon of the mashup editor as a whole is that it's an example of a class of application that has totally bypassed the "packaged software" phase. Although one could well imagine, in a previous age, some software company selling a mashup generator for installation on a developer machine and private server, it's only fitting that the sort of development tool that exists purely because of web services (lower case) should itself be born and flourish on the web.
There are of course great benefits arising from letting people build their mashups online, aside from not needing to buy the software (after all, Google et al could in theory charge). There is nothing to do to deploy, there's no need to have hosting for your software etc. The advantages are plain, but since you could see similar advantages for other software it's still interesting that we have entirely skipped the installed phase. Perhaps that's yet to come? There would doubtless be advantages to that approach, too.