Q: Are there any available Mac OS X downloads available for old laptops?

Snow Leopard 10.6 (on disk): http://store.apple.com/us/product/MC573Z/A/mac-os-x-106-snow-leopard.

Lion 10.7 download: http://store.apple.com/us/product/D6106Z/A/os-x-lion.

Mountain Lion 10.8 download: http://store.apple.com/us/product/D6377Z/A/os-x-mountain-lion.

10.9 and 10.10 are no longer available. 10.11 (El Capitan) is on the Mac App Store: https://itunes.apple.com/us/app/os-x-el-capitan/id1018109117?mt=12.

What version of Mac OS do you have on it now? You said it's 2008, but what model is it (MacBook or MacBook Pro)? It is likely compatible with the latest version, El Capitan, but if you do not already have 10.6 Snow Leopard or later, you would need to upgrade to that as an intermediate step. See here for instructions: Updating Mac OS.

(Note that I may receive some form of compensation, financial or otherwise, from my recommendation or link, because some pages on the site contain small banner ads).

I suggest using OS X Internet Recovery. Restart your Mac while pressing and holding the Option and the R keys. After you have connected to Apple's servers see what you are offered as the most recent version of OS X you can install on your Mac. Most of the 2008 laptops can usually run OS X 7.5 Lion.

OS X Recovery -

https://support.apple.com/en-us/HT201314

Late 2012 Mac mini, macOS ?;  Watch, 38 mm silver AL, Watch OS 2.2.2; iPad Air 2 & iPhone 6+, iOS ?;  Apple Airport Express

Only Apple computers are compatible with Apple software, no other computer is.