Good news! When you are using MDT and/or SCCM/ConfigMgr and want to create driver packages, you can download them for Dell, HP and Lenovo systems. That saves a lot of time, because to need to download every single driver available. Let's have a look at the different methods for companies.
Dell has a website available for Driver CAB files for Enterprise Client OS Deployment. This can be used for WinPE (5.0 also!), XPS systems, Venue systems, Latitude systems, Optiplex systems and Precision systems. There are also combo packs available. They can be found here: http://en.community.dell.com/techcenter/enterprise-client/w/wiki/2065.dell-driver-cab-files-for-enterprise-client-os-deployment.aspx
Just use "Dell Client Integration Pack" to import Driver CAB files in a easy way: http://en.community.dell.com/techcenter/os-applications/w/wiki/2565.dell-client-integration-pack.aspx
HP takes the next step and provides ready-made driver packages for MDT and SCCM for the business models of notebooks, desktops and workstations. The packages can be obtained via SoftPaq Download Manager (SDM) or from the HP support website. It appears they are primarily for the current generation of products. To get the download manager, navigate to the HP manageability website: www.hp.com/go/easydeploy or directly to www.hp.com/go/sdm
Lenovo has a website available for "Microsoft SCCM and MDT Package Index". This can be used for ThinkCentre systems, ThinkStation systems and ThinkPad systems. Packages provide the device drivers in .inf form for, in order to allow you to deploy Windows images with SCCM by importing the device drivers. These driver packs are also supported with MDT. They can be found here: http://support.lenovo.com/en_US/downloads/detail.page?DocID=HT074984
Really great to see that known vendors has support for MDT and/or SCCM/ConfigMgr now!
Update: HP Client Integration Kit for ConfigMgr 2012 R2