WARNING Using TrueCrypt is not anymore secure as it may contain unfixed security issues
From May 2014 developers discontinued Truecrypt and suggest to migrate from TrueCrypt to BitLocker
If your computer is fast enough and/or the main aim is the security a solution can be to install an encrypted virtual machine (vmware or virtualbox Qemu...or any of the Hypervisor) that presents some advantages as you can read in Is dual-booting an OS more or less secure than running a virtual machine?
Nowadays it exists a wide range of programs that allows to create an encrypted partition.
It's possible to give a look to the list in wikipedia choosing among the operative system on which they reside, their licence (Proprietary, GPL, BSD, Open Source...) and the features they provide
Hidden containers: Whether hidden containers (an encrypted container (A) within another encrypted container (B) so the existence of container A can not be established) can be created for deniable encryption. Note that some modes of operation like CBC with a plain IV can be more prone to watermarking attacks than others.
Pre-boot authentication: Whether authentication can be required before booting the computer, thus allowing one to encrypt the boot disk.
Single sign-on: Whether credentials provided during pre-boot authentication will automatically log the user into the host operating system, thus preventing password fatigue and reducing the need to remember multiple passwords.
Custom authentication: Whether custom authentication mechanisms can be implemented with third-party applications.
Multiple keys: Whether an encrypted volume can have more than one active key.
Passphrase strengthening: Whether key strengthening is used with plain text passwords to frustrate dictionary attacks, usually using PBKDF2.
Hardware acceleration: Whether dedicated cryptographic accelerator expansion cards can be taken advantage of.
Trusted Platform Module: Whether the implementation can use a TPM cryptoprocessor.
Filesystems: what filesystems are supported.
Two-factor authentication: Whether optional security tokens (hardware security modules, such as Aladdin eToken and smart cards) are supported (for example using PKCS#11)