Does she have a treat toy like a kong? Those, or a safe bone if you feel comfortable with it are nice for rainy days. If you have a space inside where she can run safely, you could let her chase treats. Have her sit next you you, then throw the treat down the hall. When she gets it, call her back to you and give her another one, then repeat the process. When my dog plays this game, we have to slow him down sometimes because he'll try to run while eating, and we're afraid he might choke. You can also hide treats and toys in a room, and let her sniff them out. If it's cold out we also do some of the dog IQ tests. Not to test his intelligence but because puzzles can tire a dog out too. You can find a lot on google.
The ones I remember off hand are: putting a treat under a cup on the floor, and letting him figure out how to get it, putting a treat in an empty pop bottle, and letting the dog learn how to dump it out, or putting a treat in an empty toilet paper tube, crimping the sides and letting the dog get it out (careful, this last one might result in lots of shredded paper, or eaten paper if your beagle is into that). See a theme here? /forums/images/%%GRAEMLIN_URL%%/wink.gif Most beagles will work really hard if there's yummy smelling food involved.