The Wellcome Genome Campus gives regularly offers online classes on genomics, bioinformatics, etc. that are certified and FREE.
This class looked especially relevant: https://coursesandconferences.wellcomegenomecampus.org/our-events/bacterial-genomes-dna-protein-function-bioinformatics-online-aug19/
https://www.sanger.ac.uk/news/view/new-online-course-introduces-bioinformatics-address-skills-gap
Here is an interview with Dr Pamela Black, Education Lead, Advanced Courses and Scientific Conferences, Wellcome Genome Campus, about these free courses: https://www.nature.com/articles/d42473-019-00209-1
You can sign up for their newsletter on this page to receive notices about new classes:
https://coursesandconferences.wellcomegenomecampus.org/event-type/online-courses/
edX has a course taught by one of the creators of rosalind.infothat can be audited for free for a short time (about a month)
Coursera Course by him also, :
If you don't have a biology background -- this course has online video lectures:
A bioinformatics treasure hunt: https://www.ebi.ac.uk/training/online/course/10th-anniversary-treasure-hunt
Personal Webpages and Blogs of Bioinformaticians
There's really only the one post in the last blog, but he lists a lot of links (and recommends rosalind.info!)
https://bitsilla.com/blog/2016/12/bioinformatics-starter-pack-getting-started-in-bioinformatics/
This last one seems to be full of helpful advice and resources.
Guides and Cheatsheets
The Carpentries -- workshops teaching R, Python, Git, Unix, Data Analysis
I started learning Python at one of these workshops and got certified as one of their trainers. I have helped at a number of their workshops at the University of Washington.
Look here to see where upcoming workshops are located:
https://carpentries.org/upcoming_workshops/
There is even one coming up in GERMANY on October 16th:
Online Bioinformatics Courses Available to Audit -- paid certificate option also available
https://courses.edx.org/dashboard/programs/293931fa-67b2-4c2e-9a44-c53c215f50d8/
Interactive Activity on Gene Expression: https://media.hhmi.org/biointeractive/click/genetic-medicine-interactive/