If you still insist in opening your laptop at the coffee shop, here are some freeware (donationware) that you can use to protect your files.TrueCrypt
This is free (donationware), open source "virtual drive" encryption software, and it's available for Windows, Mac OS X, and Linux.
DiskCryptor
DiskCryptor is a derivative of TrueCrypt, which is tailored for full drive encryption. It is particularly good for removable devices like USB flash drives.
FreeOTFE
FreeOTFE is also an open source disk encryption program. It operates exactly like a normal disk, except that anything written to one of them is encrypted.
OpenSSL File-encryption
This encryption now works on Windows, not just Linux.