HP LaserJet 5L and Airport Extreme Printing
The HP LaserJet 5L is not supported for use with the Airport Express/Airport Extreme Base Station with HP's own printer driver.
It will work with the ljet4 driver built into Ghostscript.
You must add the printer using IP Printing and the socket/JetDirect printer type, to IP address 10.0.1.1 (assuming your Airport Express is at its default IP address).
Although the linuxprinting.org site recommends the hpijs driver, some people have found that it doesn't handle 600 dpi very well with the amount of memory in a stock LaserJet 5L. Even moderately complex pages are printed out with at least a part of the page rendered at a lower resolution, a tell-tale sign of low memory with this printer.
Thanks to Alan Somers for the information.
Follow-up from Alan
The ljet4 driver has been working pretty well, but I've been experiencing occasional artifacting, especially when the print output was scaled
Last week, I started looking around on eBay for a memory card for the printer in hopes that I could switch to HPIJS to eliminate the artifacts. I found an 8 MB card for $27 shipped, so I decided to buy it. It came yesterday and I did some comparison prints of a brochure with and without the memory card and using both drivers.
The results were astounding. Not only did the extra memory allow the printer to print cleanly at 600 dpi with the HPIJS driver, but the output of the ljet4 driver was also much sharper. Apparently, the printer had been "downshifting" to 300 dpi on at least some printouts the whole time I was using ljet4. I didn't notice any artifacting on the test document in any of the test configurations, but I can't help thinking that the artifacts were a side effect of the "downshifting".
As a side note, my theory on why the HPIJS driver had so much more difficulty than the ljet4 driver under the low memory condition is that HPIJS appears to do its own grayscale dithering whereas ljet4 appears to rely on the dithering built into the printer. There's an obvious randomness to the HPIJS gray areas compared to the fine cross-hatching produced by ljet4. By allowing the printer to handle the grayscale shading, ljet4 could optimize its output whereas HPIJS was essentially outputting a bitmap.