BioRxiv and MedRxiv (pronounced bio-archive and med-archive) are shaping up to become the most prominent preprint servers in the biological and medical sciences, respectively. Some researchers are already using these servers as the most efficient and instantaneous avenue for disseminating cutting edge results.
A new platform - Outbreak Science Rapid PREreview (OSrPRE) - is an open source and free platform for the crowdsourcing of rapid reviews of outbreak-related preprints. Rapid reviews are open (but with the option of being anonymous) and structured high-level reviews designed to capture the importance and quality of the research. Rapid reviews by different reviewers are aggregated and visualized across many reviews. If you are a researcher or healthcare practitioner with the relevant expertise, please consider reviewing 3 COVID-19 preprints on OSrPRE. On the website, you can copy/paste the DOI of the preprint of choice and either request or review it on OSrPRE. Additionally you can use the available browser extensions and add preprints and reviews as you browse.  
Authorea also has a preprint repository for preliminary research findings; it is integrated with Wiley Open Research titles: authors submitting to these journals can opt to make their submission publicly available as a preprint. The repository is not domain-specific: it ranges from quantum chemistry to ecology, and from artificial intelligence to obstetrics and gynaecology. In the last few weeks, a number of preprints about the coronavirus have appeared (browse all #covid-19 preprints here) and we are posting one Covid-19 preprint per day on Twitter. Important benefits of Authorea as a preprint server are: (1) preprints are in HTML format, (2) preprints can host data and code, (3) there is a public commentary feature, increasing community-wide collaboration and promoting discourse.