Ethereal also comes with tethereal which will run fine from just a tty. You can also use tethereal (or another packet sniffer such as tcpdump or snoop) to dump traffic to a file and then pull the results back to your local machine to dissect them using the full power of the Ethereal GUI.

Update: Just to clarify, tethereal has no X parts and will spit out most of the same information as ethereal can:

  0.021897 199.242.139.15 -> 199.242.139.11 HTTP HEAD / HTTP/1.1

0000  00 10 4b 66 c1 93 00 e0 29 27 1a ae 08 00 45 00   ..Kf....)'....
+E.
0010  00 a8 c2 54 40 00 3f 06 d2 fb c7 f2 8b 0f c7 f2   ...T@.?.......
+..
0020  8b 0b d8 89 00 50 67 3b 94 99 0d bf 1c 41 80 18   .....Pg;.....A
+..
0030  82 18 89 7b 00 00 01 01 08 0a 07 2d 1c 04 07 2d   ...{.......-..
+.-
0040  1c 02 48 45 41 44 20 2f 20 48 54 54 50 2f 31 2e   ..HEAD / HTTP/
+1.
0050  31 0d 0a 54 45 3a 20 64 65 66 6c 61 74 65 2c 67   1..TE: deflate
+,g
0060  7a 69 70 3b 71 3d 30 2e 33 0d 0a 43 6f 6e 6e 65   zip;q=0.3..Con
+ne
0070  63 74 69 6f 6e 3a 20 54 45 2c 20 63 6c 6f 73 65   ction: TE, clo
+se
0080  0d 0a 48 6f 73 74 3a 20 70 68 79 64 65 61 75 78   ..Host: phydea
+ux
0090  2e 6f 72 67 0d 0a 55 73 65 72 2d 41 67 65 6e 74   .org..User-Age
+nt
00a0  3a 20 6c 77 70 2d 72 65 71 75 65 73 74 2f 32 2e   : lwp-request/
+2.
00b0  30 31 0d 0a 0d 0a                                 01....

  0.027344 199.242.139.11 -> 199.242.139.15 HTTP HTTP/1.1 200 OK

0000  00 e0 29 27 1a ae 00 10 4b 66 c1 93 08 00 45 00   ..)'....Kf....
+E.
0010  00 ec c2 55 40 00 40 06 00 00 c7 f2 8b 0b c7 f2   ...U@.@.......
+..
0020  8b 0f 00 50 d8 89 0d bf 1c 41 67 3b 95 0d 80 18   ...P.....Ag;..
+..
0030  82 18 a6 de 00 00 01 01 08 0a 07 2d 1c 05 07 2d   ...........-..
+.-
0040  1c 04 48 54 54 50 2f 31 2e 31 20 32 30 30 20 4f   ..HTTP/1.1 200
+ O
0050  4b 0d 0a 44 61 74 65 3a 20 4d 6f 6e 2c 20 32 30   K..Date: Mon, 
+20
0060  20 53 65 70 20 32 30 30 34 20 31 36 3a 32 31 3a    Sep 2004 16:2
+1:
0070  34 35 20 47 4d 54 0d 0a 53 65 72 76 65 72 3a 20   45 GMT..Server
+:
0080  41 70 61 63 68 65 2f 31 2e 33 2e 33 31 20 28 55   Apache/1.3.31 
+(U
0090  6e 69 78 29 20 44 41 56 2f 31 2e 30 2e 33 20 6d   nix) DAV/1.0.3
+ m
00a0  6f 64 5f 70 65 72 6c 2f 31 2e 32 39 20 6d 6f 64   od_perl/1.29 m
+od
00b0  5f 73 73 6c 2f 32 2e 38 2e 31 39 20 4f 70 65 6e   _ssl/2.8.19 Op
+en
00c0  53 53 4c 2f 30 2e 39 2e 36 65 0d 0a 43 6f 6e 6e   SSL/0.9.6e..Co
+nn
00d0  65 63 74 69 6f 6e 3a 20 63 6c 6f 73 65 0d 0a 43   ection: close.
+.C
00e0  6f 6e 74 65 6e 74 2d 54 79 70 65 3a 20 74 65 78   ontent-Type: t
+ex
00f0  74 2f 68 74 6d 6c 0d 0a 0d 0a                     t/html....
[download]

But you can't do things like use the "follow this connection" tool which the Ethereal GUI provides.

Okay, but correct me if I'm wrong, but you still need a GUI for that, right? Some people just don't have one available to them. I, for example, don't have one available to me right now because I'm in the process of updating my GUI software -- not that I'd use a GUI for packet sniffing, or any system administration anyway.