My Recommendations: First of all let me make a short list of the manufacturers that most PSU specialists recommend:
Antec
OCZ
Fortron (FSP Group)
Zippy
Enermax
Seasonic
Raidmax
Vantec
Silverstone
Thermaltake
PC Power & Cooling

As far as specific power supplies:

Entry
-Fortron AX400-PN $39.99
18A and 16A on dual +12V rails. 40 Dollars. Need I say more? For any gamer on a budget, this is the way to go.
-Antec SmartPower 2.0 SP-500 $68.99
Strong dual +12V rails and wide availability make this power supply very nice, and for $70 it cannot be beat.
-Antec TRUEPOWERII TPII-430 $69.99
My local PC shop uses these religiously, and for good reason. An excellent supply for even a middle range system, the TruePower series from Antec is a very solid choice.
-ENERMAX EG425P-VE SFMA 2.0 $69.99
A nice looking PSU with plenty of ability to power basic systems

Mid-Range
-Fortron AX450-PN $49.99
The 450W version of the aforementioned Fortron power supply. This one has greatly improved amperage on the +3.3V and +5V rails, making it more suitable for older (AGP based) computers. It also adds an extra 2A to the 2nd +12V, fully capable of powering your gaming machine, and for only $50.
-ENERMAX EG651P-VE FM(24P) $108.99
The only thing I can even imagine being able to stress this power supply is a high-end system running heavily overclocked, or a SLI system with 2 7800GTX's or something insane like that. 36A on the +12V, come on. For people looking at this type of power supply (one strong +12V), also consider the OCZ PowerStream OCZ520ADJSLI.
-Antec TruePower 2.0 TP2-550 $99.99
A step up in the excellent TruePower 2.0 series.

High-End
-PC Power & Cooling 510 SLI-PFC $219.99
Absolutely the best quality power supply available. SLi certified for your insane gaming setups, and top-notch customer support in the unlikely event of a problem.
-ENERMAX EG851AX-VH(W) $235.99
Enermax's top of the line. 3 +12V rails, 2 with 18A, and one left over for anything else after SLI. This power supply will do well with any system.

Ultra High-End
-PC Power & Cooling 850 SSI SLI $499.99
When money is not an object, this power supply is simply the best. Very expensive, very powerful, and most people that have used/reviewed it say it is worth every penny.

( SEVERAL RECOMMENDATIONS ADDED AND PRICES UPDATED BY SHOES ON 1/14/2006)

CREDITS:
Although all of the thoughts and opinions expressed in this article are genuinely mine, I would be remiss to even hint that I put together this article unassisted. Complementary information was gathered from

Powering Your PC: A Guide to Power Supplies (May 18, 2005) Jason Rabel. ExtremeOverclocking.com
Switched-mode power supply (August 29, 2005) Wikipedia.org

Thanks to David Hammock, A. John Mallinckrodt, Christian "ZeGermans" Koebel, and The PC Guys in Corona, CA for helping, in one way or another, with this article.