I've just intalled:

Lubuntu 13.04
latest versions of Chrome, Chromium, Opera and Firefox
Flashplugininstaller 11.2
Lubuntu restricted extras

If I disable the flashplugin in chrome plugins I can see few videos on youtube.

sudo lshw -C cpu
description: CPU
product: AMD Duron(tm) processor
vendor: Advanced Micro Devices [AMD]
physical id: 4
bus info: cpu@0
version: 6.8.0
slot: Socket A
size: 1596MHz
capacity: 3GHz
width: 32 bits
clock: 133MHz
capabilities: fpu fpu_exception wp vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 mmx fxsr sse syscall mmxext 3dnowext 3dnow cpufreq

I installed two extensions in chrome:
HTML5ify and HTML5 video for youtube.

I don't know if I can do something better to see flash videos on other websites different from youtube.