StarFall (It looks kinda ugly but it's an amazing site)
Explode the Code workbooks or online program.
Games for Reading book. (Lots of great games & activities that a parent/teacher can prepare for the child.)
And specifically for letter sounds check out the Logic of English apps and Leapfrog Letter Factory.
A lot of these are not websites, but you come from Montessori so I figured you might be interested in other stuff that's more hands on.
Reading:
StarFall (It looks kinda ugly but it's an amazing site)
Explode the Code workbooks or online program.
Games for Reading book. (Lots of great games & activities that a parent/teacher can prepare for the child.)
Handwriting:
I plan on teaching italics instead of cursive & manuscript so the only non italic site I can recommend is Handwriting without Tears (and not cheap).
Italics, Beautiful Handwriting for Children (pdf book with printable pages)
Getty-Dubay Italic Handwriting
Or something more fun, Draw Write Now.
Math:
Education Unboxed (paired with Cuisenaire rods)
MEP Reception (full curriculum previously used in schools. highly recommended in the homeschool world)
> Living books are usually written by one person who has a passion for the subject and writes in conversational or narrative style. The books pull you into the subject and involve your emotions, so it’s easy to remember the events and facts. Living books make the subject “come alive.” They can be contrasted to dry writing, like what is found in most encyclopedias or textbooks, which basically lists informational facts in summary form.