Actually usefull

SSH client, GPL

WirelessIRC -- install, GPL

Compass, GPL

Useful, non-free

opera mini

GPS software

Other

Check: http://destilapps.wz.cz/cz/eurotelsms.html, GPL, plus has dictionary there, too.

Virca IRC client, GPL

jmIRC client -- install, GPL, smaller than other two.

Global time -- install, shareware

Programmable calculator -- install, maybe he'll open source it if enough people mail him? Reverse polish notation

VNC client, install, GPL

bookshelf ebook reader, GPL

bearlib, includes web (subset) browser, Artistic license. Unfortunately web browser is not really usable on its own, things like progress indication and back button are missing.

OGC WMS client, map viewer, free for non-commercial use.

Tools like display-a-key and system info, MIT

MobileBG -- backgammon, GPL, install

JamTris, tetris, install, GPL

MicroSky, install, freeware

Some tools for game development (portable accross desktops and j2me) are at jtgl. SyncML tools (including j2me) are at sync4j.

ReqWireless web browser and mail client -- web browser could be quite nice, but shareware licence makes it unusable.

There's quite nice collection of applications at www.getjar.com. Go wap.getjar.com|quick download|. Applications (tested on k700i):

J2MExed 71 (error "invalid application") 
TBlocks 293 (block-out, nice!)
Cubes3D 165
fremtris 235
sokojava 232 (nice)
hangman 383 (unfortunately letters are selected by arrows :-()
minesweeper 33
reference 619 (ugly shareware delay at startup, and web browser is probably more usefull, also their server does not work.)
mcalculator 525 (control is "interesting" but better than build-in),
periodicTable 572 (wow, actually quite nice)
e300 food advisor 332 (nice, usable search)
timetracker 37
timers 21
calculator 84 (based on entering C-like expression; pretty hard to use on phone)
midp sys info 549 ("invalid application")

Mobario, impossible to install, authors are bunch of idiots blocking direct download and requiring daily key

MobileBASIC, install, shareware (examples: calculator)

SiWeb browser - I did not find out how to make it work

Tlappy, strip (not too funny :-()

Another mail reader, works through proxy server

bemused for java looks pretty interesting.

Non-free software

http://stahuj.mobilfiesta.cz - map of czech republic.