Ask HN: are there any website equivalents of "Show HN"?

The 'Show HN' convention seems to have emerged from the community rather than being a feature created by the site owners. It also appears that not everyone agrees on the one convention: sometimes 'Show HN' posts appear on the home page (submitted as urls) and sometimes they appear in the 'ask' page (submitted as text). Also, I've noticed some people use the 'Ask HN' prefix when looking for feedback for their startup rather than Show HN

As a coder/entrepreneur I find it really interesting seeing what other new startups are being made and I especially find reading the feedback in the comments to be really useful (to make sure I'm not making the same mistakes). Show HN works really well for this but as it's not a dedicated feature of the site it can be hard to filter out the Show HN posts.

Does anyone know of any good sites dedicated to showing off new startups and getting feedback?

I've come across hackandtell.org which is a list of meetup.com groups for demoing your new startup (in person rather than online)