My daughter is about the same age as your son, and has just recently started walking. Around 12 months she started standing on her own in the middle of the room - I thought she'd be walking the next day. Boy was I wrong! It took her several more weeks just to take ONE step! Now, at just over 14 months she's walking about 1/2 of the time (maybe a little less).
Before she was walking on her own, I would hold her hands and we'd walk around like that I'd say in a sing-songy voice "Walking walking walking" and then one day when she was across the room I asked her "Can you walk? Can you show me how you walk?" and she stood up and took a step! It was so funny, but she really did get it. We also have a little push toy that she loves, but I can't say if it helped or hindered her walking...I think she was ready to start walking around the same time we got it anyway.
But overall it was a pretty slow process. People always say, you'll just look over one day and they'll be walking, but for us it wasn't like that. It's been nearly 2 months since she took her first step and she's still not walking full time. I think that it's important that you don't put too much pressure on the kids or act disappointed every time you stand them up and they drop to their knees. He really *will* walk when he's ready! And honestly, he's not late. People will say he's late, but they probably don't know that the "normal" range for walking is like 8 months to 17 months. So 14 is no where near the end of the normal range - he's got 3 whole months to go before he's considered a late walker! If he's not walking by then, it would be appropriate to talk with Early Intervention, and even then a little physical therapy would probably get him on the right track quickly.
Good luck and seriously, don't worry!