Entering "Scientific American RSS" in Firefox's url/ "awesome bar" opened this page directly:

Scientific American : RSS feeds

Pick which of their feeds you want from there.

I'm sure that if you did the same thing for any of the other similar "apps" that showed up on that OVI link from the OP, you'd get similar results.

As the others have noted, Maemo 5 comes with a quite reasonable generic RSS reader included and there are several other alternatives available - no need for site-specific RSS apps.

Have fun, good luck.