I've tried everything from facial-tissues, toilet-paper, different types of writing-paper...until I came upon a solution while at work one day.
Ordinary paper-towels.
Now I don't mean those huge never-ending rolls of paper that never seem to tear correctly when you want them to and you end up with six feet of paper to dry a pair of hands, I mean those sheets of paper-towel which are folded thrice, to form little interlocking 'N' shaped pieces of paper. They're stacked up and form rectangles.
I've found that this kind of paper is very suitable for blotting-paper. It's light, it's easy to cut/tear into suitable sizes, and it's already in long, rectangular strips, so it's easy to put into rocker-blotters (If you can't put it into your blotter, I use small pieces of sticky-tape to hold the paper in place while I put the top back onto the blotter).
But, above all, this paper is HIGHLY ABSORBENT (It would have to be!) and doesn't smear/spread ink when you use it, that is, provided you're not a klutz. I pinched two huge handfuls of the stuff from work and keep it in my desk now. I cut it up and use it for blotting-paper.
So if you're looking a free alternative to blotting-paper, try that. It works for me!
Not this:

This: