If you're looking for excellent-sounding signal processing for your projects, you might consider a hardware accelerator such as the TC Electronic PowerCore Compact (tcelectronic.com; $499) or the new Universal Audio UAD-2 Solo/Laptop card (uaudio.com; $499 to $799 depending on plug-in bundle; see Fig. A). The former connects to your laptop using FireWire, and the latter through the ExpressCard/34 slot (also known as the PCMCIA slot). Because both units supply their own DSP, you can add effects through them without maxing out your laptop's CPU.
Not all laptops have an ExpressCard slot. Apple MacBook Pros do, but regular MacBooks don't. Because the new MacBooks don't have FireWire either, you're out of luck for running either the UAD or PowerCore devices on those machines.
On the PC side, many laptops now come with ExpressCard slots. Most have the larger ExpressCard/54 slots. The UAD-2 Solo/Laptop card is compatible with those as well. (Universal Audio includes an extender that fits on the card to make it sit more firmly in the slot.)
Both the UAD-2 Solo/Laptop and the PowerCore Compact come bundled with a range of plug-ins, and more can be added. The Solo/Laptop's plug-ins lean heavily toward emulations of classic hardware such as Pultecs and 1176s. The PowerCore's plug-ins run the gamut from hardware emulations to channel strips and even a synth.