Addition and concurrence
and
not only...but also
besides
moreover
also
furthermore
in addition

Alternative idea
or
either...or
otherwise
instead

Similarity
like (prep.)
as...as
likewise
similarly
in like manner

Concluding, summarizing
In short,...
In conclusion,...
In other words,...
To sum up,...
To recapitulate,...

Contrast
than
not as/so ...as
but
while (informal)
however
by/in contrast
on the contrary
on the other hand
whereas (chiefly used in formal legal documents)

Negation
nor
neither...nor

Condition
if
if...then
unless
whether

Transitions
Now that we have..., let us take a closer look at...
Let us turn our attention to...

Backward pointers
This / These
The above-mentioned...

Cause-effect and reason-result
because
since
as
for
so
therefore
consequently
accordingly
hence
thus
for this reason
as a result

Purpose
so that
in order that

Closer Focus, supporting details and examples
in fact
for example
A good example of this is...
To illustrate,...
Let us take a closer look at...

Concession,
Assertion contrary to expectation
although
even though
though
yet
but
still
nevertheless
nonetheless
however that may be
in spite of the fact that
however much

Sequence (time)
first, second, etc.
in conclusion
in the meantime
then
thereafter
subsequently

Paraphrasing
In other words,…
…, or…,

Postponing
I will address / deal with / discuss / examine this in more detail below, but first...