I've been very lucky with a couple of lines I wanted to trace forward. I had a couple of daughters born in the late 1890's to families in Durham.
Using the superb Durham County Council site, I was able to guesstimate marriages in the 1920's and 1930's (as Timbottawa did with 1837Online). I found two possible marriages for each daughter, and because the Durham site gives you the spouses deatails, I was able to check these with my mam. She wouldn't have been a able to tell me their surnames unprompted, but given a choice of a couple, her memory was jogged. I was then able to search the Durham site for likely births in the few years after the marriage, and that way add a few extra names to my tree.
cheers
Paul