Though it is unfortunate that Apple decided to hide the Library folder on new installs of Lion, there are a couple of ways to still access your library folder.
The first is using the Go menu in the Finder. If you click on the Go menu at the top of the screen while using the Finder and select 'Go to Folder...' (or use Command, Shift, G key combo) and then type in '~/Library' without the quotes, it will open your library folder for you. You can also use the key combo to get the Go window to pop up in an open dialog which is used when you use the File>Open menu command.
The second would be to tell Os X to show it again. There are some good simple instructions on it here:
http://osxdaily.com/2011/07/04/show-library-directory-in-mac-os-x-lion/If you still would rather not store your Accounts file in the Library, you can now change where the data file is located via CheckBook's preferences.