Say one day you’re feeling particularly frugal—or ambitious—so you decide to install a garbage disposal yourself instead of hiring a plumber. It seems like a great idea…until the water starts gushing from below the sink. Avoid such catastrophes by perusing the website diyornot.com, run by DIY veterans Gene and Katie Hamilton, who have written a syndicated newspaper column on the subject for more than 20 years. Their free Web tool or mobile app allows you to search for a project and find out the relative cost (specific to your ZIP code) and the time it would take to do it yourself compared with hiring a professional. The site’s database also provides information for more than 300 home projects, like repainting cabinets and installing a dimmer switch. And it offers basic instructions and a list of the supplies you’ll need if you decide to tackle the task on your own.