Addition: in addition, again, moreover, further, furthermore, finally, lastly, at last, in conclusion, first, second, in the third place (not firstly, secondly, and so on), once again
Comparison: similarly, likewise, in like manner, whereas, but, on the other hand, except, by comparison, where compared to, up against, balanced against, vis-a-vis
Contrast: but, however, yet, still, nevertheless, on the other hand, after all, for all of that, on the contrary, notwithstanding, in contrast
Emphasis: in fact, indeed, in any event, certainly, definitely, never, extremely, absolutely, always, forever, perennially, eternally, emphatically, unquestionably, without a doubt, certainly, undeniably, without reservation
Example: for example, for instance, in this case, in another case, on this occasion, in this situation, take the case of ..., proof of this, evidence of this, thus, in this manner
Exception: yet, still, however, nevertheless, in spite of, despite, of course, once in a while, sometime
Place: near, beyond, opposite to, adjacent to, at the same place, here, there
Proof: for the same reason, obviously, evidently, furthermore, moreover, besides, indeed, in fact, in addition
Purpose: to this end, with this object, for this purpose
Result: accordingly, thus, consequently, hence, therefore, wherefore, thereupon
Sequence: first, second, third, A, B, C, 1, 2, 3, next, then, following, this, at this time, now, at this point, after, afterward, after this, subsequently, soon, finally, consequently, before this, previously, preceding this, simultaneously, concurrently, at this time, therefore, hence
Summary: in brief, on the whole, in sum, to sum up
Time: at once, immediately, meanwhile, at length, in the meantime, at the same time, in the end, in the interim, then

Source: Parker, John F. (1982) The Writer's Workshop. Don Mills, Ontario: Addison-Wesley, pp. 227-228.