Those few general slim desktops on the market are trending towards more and more value oriented offerings. Of them, the Acer Aspire AXC600 offers a nice package that is priced as low as $310. The dual core Pentium G2020 processor, 4GB of memory and 500GB hard drive make this a capable system for the average user that it looks to browse the web, watch media and maybe do some productivity applications. The one big downside to the system is that it does not feature any USB 3.0 ports making it less suitable for those that might need to add extra storage. A good alternative in this case is the slightly more expensive Dell Inspiron 660s which is priced around $400 for nearly the same features but with two USB 3.0 ports.
Apple's tiny Mac Mini system may be due for an update soon but it still remains one of the best of the mini computers. Of course, Apple doesn't have much competition in this segment anymore as most of the tiny PCs have either switched to the slower ATOM based systems or compact designs that cost as much or more than Apple. The diminutive mini is not much bigger than a stack of a few CD cases yet packs some solid features making it an excellent home theater PC as long as you don't need an optical drive. The biggest downside is the limited 500GB hard drive but the updated version does feature four USB 3.0 ports plus a Thunderbolt port for nice external storage options. At $550, it is somewhat pricey for the features but it is hard to top such a tiny PC.
As more companies have either dropped general purpose small desktops or shifted to the budget segment, there is a big gap for those wanting a small desktop with a bit more features. The Alienware X51 may have originally been designed as a small gaming system but it also offers a very capable slim desktop system for those that just want a smaller PC. The $850 version offers a quad core i5 processor, 8GB of DDR3, 1TB hard drive, dual layer DVD burner and even an NVIDIA GeForce GT 645 for light gaming or accelerating non-3D programs. The only downside is that the compact size is generated by having a larger external power brick. A suitable slim system that doesn't feature a large external drive is the Dell Inspiron 660s although it only comes with integrated graphics and lower performance processors.
Small gaming desktop systems are a new trend in the market thanks to the higher prices they can generally bring. The iBUYPOWER Revolt R570 is an amazingly capable gaming platform that has a price tag of under $870. This performance comes from a combination of a i5-3570K quad core processor and a GeForce GTX 650 graphics card that let it play modern games at full 1080p high definition resolutions without a problem. The system is a bit bigger than the competition and can be noisier when running under load. For those that want the best and are not as concerned about price, the Falcon Northwest Tiki is spectacularly built system that can have some incredible power but be prepared to pay as it starts around $1700 and goes up from there.