For OS/2, check out [url="[url]http://www.mozilla.org/ports/os2/"[/url];]Warpzilla[/url]. It's probably not as small and lightweight as K-Meleon, though...
Better may be [url="http://www-4.ibm.com/software/os/warp/browser/"
;]IBM Web Browser for OS/2[/url].
Apparently there has been [url="[url]http://www.geocrawler.com/mail/thread.php3?subject=DOS+Mozilla%3F&list=120"[/url];]some discussion of a DOS port[/url] (5 years ago), but it seems to have died out. I guess it wasn't feasible. [url="http://www.cc.jyu.fi/~jvkujala/raportti/node8.html"
;]DOSzilla[/url] looks like a dead project.
A text-based browser (like [url="[url]http://lynx.browser.org/"[/url];]lynx[/url]) would probably run better on DOS-based machines. For OS/2, consider [url="http://www.opera.com/products/desktop/index.dml?platform=os2"
I hope all my links work. If they don't, I apologize for the messy post :-)