Hi, since
http://packages.slackware.it is in "stay tuned" from a while i wrote a simple Slackware package browser, you can find it here:
http://spb.twopenguins.it/go.spb
It search packages and files in various Slackware's versions (i'll add more) standard tree (a, ap, ecc) plus packages in patches/.
If someone have something to suggest or a bug to report please email me or reply here.
I hope i did something useful.
Thanks