The short answer
RevenueBug lets founders publish provider-reported revenue and a daily history on a public profile, then optionally mark the startup For sale to receive private inquiries. SideProjectors is a marketplace where makers list side projects for sale, including SaaS, apps, browser extensions, blogs, and domains, and can also showcase a project or look for a co-founder. RevenueBug starts from connected revenue data; SideProjectors starts from the project listing, including projects that may not have revenue yet.
How they compare
When RevenueBug fits
RevenueBug fits a founder whose product already earns money through a supported provider and who wants buyers or peers to see that revenue history. The profile can stay public whether or not the startup is for sale.
When SideProjectors fits
SideProjectors fits makers selling a small or early project, including pre-revenue tools and domains, or looking for a co-founder or feedback. Its site says submissions are reviewed before approval and that basic submissions and browsing are free.
Using both
A maker could list a project on SideProjectors and link to a RevenueBug profile so interested buyers can see provider-reported revenue history. Buyers should still confirm the underlying records and the transfer terms.
Features and terms can change. Check the linked primary sources before choosing a platform.