Haven't been punting in Stockholm myself, but I still have a few tips.
Two websites: eskortflickor(dot)net and realescort(dot)se. The first is a site linking to other escorting sites of varying quality.
There are also some reviews, but they are not guaranteed to be reliable. Most pics are fake. Still, worth to check out. The other one (realescort) is better. Girls pay for ads, free for punters. No need to register unless you want to use the pm function or write reviews. There are moderators cleaning out the most blatant shit, still you should be careful. The girls may disable reviews, always a bad sign. Real photos are marked by the site, I'd say reliability of those so marked are somewhat better. Still, no guarantee (I am assuming it's girls you're looking for, these sites also have TS if that's your thing). Use caution, as always.

Remember punting (but not prostitution) is illegal in Sweden, getting caught carries a sizable fine.

I'm sure I don't have to tell you to avoid streetwalkers. It's also wise to avoid black girls for many reasons, not the least being they are often coerced.

(btw, if Coco, a Czech 21-year-old, happen to be there be sure to pay her a visit. She sometimes work in Sweden, and is top notch.)

If you happen to be in Oslo at some point I can give you some recommendations. I'm on a basic membership, but I'll check back on this thread.

Best of luck.