I recently went back to look at my old baseball card collection from years and years ago. I found some cards that might be worth something, but I'm not sure how to check. Are there any free sites online I can go to?
Here are some of the cards (all of which are mint or near mint condition)...

Barry Bonds, Topps, 11T, 1986 Rookie Card
Barry Bonds, Topps, 320, 1986 Rookie Card
Randy Johnson, Score, 77T, 1988 Rookie Card
Tom Glavine, Topps, 779, 1987 Rookie Card
Jeff Bagwell, Score, 1996, "Numbers Game", 7 of 30, gold-print card
Mike Scott, Topps, 100T, Autographed, 1983
Nolan Ryan, Topps, 770, 1992 Stadium Club edition card
Nolan Ryan, Donruss, 154, 1988
Nolan Ryan, Topps, 106T, 1989

These are just a couple of the cards. I also have a few Craig Biggio rookie cards, Jeff Bagwell rookie cards, Piazza, Kent... Where can I go online (for free) to check current and perhaps future values (after some make the HoF)? Not selling, but need value for Home-Owners insurance. Thanks...

Besides Becketts, you can try Tuffstuff.com. Their website has a free archive of card values that don't appear in their monthly magazine listings.

I'd try Beckett.com Becketts has been the gide to pricing sports collectables for many years. Remember that this is nly a guide. The value of your cards depends on several things such as colour of the card,how clear the printing is, is it centered on the sheet, does it have bent corners or creases.
But if you ask the people at Becketts they should be able to help.

Go to Ebay and see what they are going for, I said before something is only worth what someone else is willing to pay for it. Becketts may say this and tuffstuff may say that but you may run into a huge Tommy Glavine fan and he might pay more for that card than they say it is worth. Hang on to it cause Glavine will be the last 300 winner for some time.