Hi A.,
I went through this with both my boys...except they learned how to stand up quite a bit earlier--they learned to walk at 9 1/2 and 8 1/2 months, respectively, and if I remember correctly they could both stand up at 6 mos. We would just put them down for naps as usual in the crib. Yes, they got a kick out of standing up, then falling (and subsequently banging their heads) but after a couple days they got accustomed to their newfound ability to stand and would go to sleep as usual. Standing is a big novelty for your son right now, just as all his other milestones were, but in a few days he should lose interest somewhat. Just lower the crib mattress as far down as it will go for safety.
The thing to watch out for is when you see him actually trying to climb over the rails. Make sure there is nothing right next to the crib he can try to climb out on (dresser, changing table, etc.) and pay attention to when he can actually get a leg up and over the railing. It should be a while because he's such a little guy, but in case he is like my boys it could be very soon. When he learns to climb out either get him a toddler bed or one of those crib tents to prevent him from climbing out. You can see an example of one here: http://www.onestepahead.com/pwr/product-reviews/4065/Prod...
As you know, standing is a big step toward walking. If you haven't already it's time to baby proof the house for a walking baby. Make sure that sharp corners like the ones on coffee tables are covered and that your household environment discourages climbing. And keep in mind, too, that he's going to get quite bruised up in the months to come what with all the falling, running, etc.--and if he's a rowdy guy like mine, his share of injuries will be that much greater! Kids are resilient, though, so try not to worry too much ;)
Good luck, hope this helped!
--M.