I've posted this before, but given this is the Christmas buying season, perhaps it might be helpful again.
In purchasing an HD-compatible LCD TV, here are some things to look for:
1. Resolution of at least 720 pixels vertically (typically 768) and 1280 horizontally. This supports the lower of the HDTV resolutions, 720p (progressive scan), natively. It also supports the higher HDTV resolution of 1080i (interlace scan), which is 1080 pixels vertically (typically 1200) by 1920 horizontally, by scaling. And of course, it can support the lower resolutions of standard definition (SDTV 480i x 640) and enhanced definition (EDTV 480p x 854) by scaling. There are no Airstream-sized LCD TVs I know of that support 1080i natively (i.e. have that many pixels). Nevertheless, when they do appear, they will also support the lower HDTV and SDTV resolutions through scaling.
WARNING: There are some SDTV and EDTV TVs advertised as HD-compatible. They typically have one input for that, and they scale down or crop the HDTV video to fit the SDTV or EDTV resolution.
2. Component video input, also known as YPbPr. Current DVD technology stores data in Component format, and for the best picture, that's the connectivity you want to use. Using S-Video or worse, Composite video, to transmit these signals degrades the quality. Component video is an analog signal while HDTV from terrestrial or satellite broadcast, or cable, is digital. Most HDTV source boxes, such as tuners and cable boxes, convert that to analog Component that can be used by TVs that only support this standard.
WARNING: Not all TV Component video inputs support HDTV! Some only support SDTV, which is what is stored on current technology DVDs. Read the specifications carefully.
3. HDMI input. This advanced standard for connecting HDTV sources to TVs is a digital signal, and now the standard. It carries both video and audio, compared to the interim standard that was DVI-HDCP (also digital), which carried video-only. HDMI is backwards compatible with DVI-HDCP, meaning TVs with HDMI can support all features of both. DVI-HDCP and HDMI support copy protection. There is the strong possibility that future HDTV sources may not output copy-protected material over non-copy protected outputs, such as analog Component.
WARNING: Not all TVs with DVI input can read and decode DVI from HDTV sources. Read the specifications carefully. Some specify that their DVI input is only for use with personal computers, a different form of DVI.
4. Number of inputs. If your TV doesn't have an ATSC digital tuner for Over-The-Air digital broadcasts, and few small TVs do at this time, you will need at least an external tuner for that, and an input for it, preferably HDMI, but at least Component. If you subscribe to HD satellite service and have a tuner for that, it probably also has an ATSC tuner in it, and the two share one TV input.
Preferably, you will use a HDMI input for this. If your TV doesn't have an HDMI input, and has only one Component video input, you will have to downgrade the quality of your DVD connection, and use the S-Video input. If your TV doesn't have S-Video input, you will have to downgrade further and use the Composite video. Keep in mind that if you still use VHS tapes, you will need a composite video input for that.
When HD-DVDs finally do come to market, the players may only support copy-protected HDMI connection. If you buy one of these, you will need an input for it.
If you are one of the rare birds who still has an S-VHS unit, or the early laserdiscs, you will need an S-Video input for these.
5. Native 12 volt
DC input. A nice-to-have, not a need-to-have. Some LCD TVs use an external AC power supply, also known as a "wall wart," which provides 12VDC on its output. These can be hooked up directly to 12VDC and save a little battery power, instead of using a 120VAC only TV through a less than 100% efficient inverter. However, if you are going to use a satellite receiver, you will have to use an inverter anyway since the receiver supplies the dish with greater than 12VDC power, and they don't make 12VDC satellite receivers.
6. Size. The width of the front of our credenza is about 18" to the curtains. To maximize the screen size that can be put in this space, look for TVs that don't have the speakers on either side of the screen.
Hope this helps,