The obvious answers in Pentax-land are the
DA*60-250 and the
D-FA-100 WR. Reviews are
HERE and
HERE.
The budget answer for the zoom is the
DA 55-300, but it's a much lower-end zoom. Still a very nice lens; Reviews
HERE.
All of the lenses I recommended above are WR, so you can shoot happily in the rain, snow, blowing sand, whatever.
For a non-WR tele-zoom, I would absolutely recommend the
Tamron 70-200. Reviews
HERE. I like the pictures from it better than the 60-250, and it has much closer focusing and it's F2.8. It's also much cheaper. It does have a very noisy screw drive autofocus, and it is not WR, and it is big and quite heavy. I still carry mine around all the time, and I love it to pieces.
You can save money by looking here in the forum in the
marketplace. Most of us here are friends, and we sell lenses to each other mostly so we can try others. I have found the descriptions to be incredibly accurate, and the sellers to be honest and helpful. The prices in the forums are usually 5-10% cheaper than ebay as well.